Yakushi Nyorai's full title is Yakushi Rurikō Nyorai, the Medicine Master Tathāgata of Lapis Lazuli Radiance. His Sanskrit name is Bhaiṣajyaguru-vaiḍūryaprabha. The name joins two ideas, "Master of Medicine" and "Lapis Lazuli Light," and he is also called Iō Zenzei (the Medicine King Well-Gone One) and the Great Medicine King Buddha. He is the Tathāgata who heals illness as the sovereign of medicine and illuminates the world with a light as translucent as lapis lazuli.

His abode is the Pure Lapis Lazuli World (Jōruri sekai) in the far east. The sutras present him as the teaching lord of an eastern pure land, forming a counterpart to Amida's Western Pure Land of Ultimate Bliss.

At the heart of this buddha stand the Twelve Great Vows he made while still a bodhisattva. The healing of illness is only one of them. Impairments of the senses, hunger and thirst, the cold of having no clothing, the injustice of imprisonment and punishment: the twelve vows take up the sufferings of body, mind, and daily life in their entirety.

In Japan, from the Asuka and Nara periods onward, Yakushi Nyorai has been enshrined as the principal deity to whom the sufferings of this present world are entrusted, from prayers for the recovery of emperors to the prayers of ordinary people for their eyes, legs, and hips. Among the Shikoku Eighty-Eight Sacred Sites, more temples have Yakushi Nyorai as their principal image than any other buddha, and the principal image of the Main Hall of Byodoji, the twenty-second temple, is this buddha.

The Bhaiṣajyaguru Sūtra teaches the twelve vows that the Medicine Buddha made while practicing the bodhisattva path. The first vow is not about curing disease.

A great vow is the fundamental promise a buddha made while still a bodhisattva: "When I attain awakening, I will without fail bring about a world like this." One can read these as vows in which, before anyone asked anything of the buddha, the buddha himself took up human suffering and put it into words.

The first vow begins with a promise to make every person a buddha equal to himself.

• First vow: universal illumination. To bring every living being to a buddha's form equal to his own body.
• Second vow: a body like lapis lazuli. To illuminate those in darkness with the translucent light of his body.
• Third vow: inexhaustible provision. That people may lack nothing they need to live.
• Fourth vow: establishment in the Mahāyāna. To guide those walking mistaken paths onto the path to awakening.
• Fifth vow: purity of the precepts. That even those who could not keep the precepts may return to purity.
• Sixth vow: wholeness of the faculties. That impairments of the senses and the sufferings of illness may be removed.
• Seventh vow: removal of illness and ease. That the body and mind of those isolated without doctor or medicine may be at peace.
• Eighth vow: transformation of women into men. To release women from the hundred afflictions borne because of their sex (a vow premised on the social assumptions of India at that time).
• Ninth vow: guidance to right view. To release beings from the nets of Māra and the bonds of mistaken views.
• Tenth vow: liberation from bondage. To release beings from imprisonment, punishment, and the injustices of royal law.
• Eleventh vow: satisfaction of hunger and thirst. For the hungry, food first. Only afterward, the taste of the Dharma.
• Twelfth vow: fine clothing in plenty. To give clothing and adornment to those without garments, tormented by heat, cold, and insects.

The twelve vows line up sufferings of daily life and society, hunger, clothing, imprisonment, that cannot be contained within the curing of disease. The order of the eleventh vow is striking. To the hungry he first gives excellent food and drink to satisfy the body, and only then establishes them in ease through the taste of the Dharma (hōmi, the flavor of the Buddha's teaching). Before preaching, feed people first. That is this buddha's way. The original text of the sixth vow lists the names of illnesses as they were known at the time; because some of those terms sound discriminatory today, only the substance is given here.

The scripture called simply "the Bhaiṣajyaguru Sūtra" exists in four Chinese translations, produced and refined over roughly two hundred and fifty years.

The word at the center of his name, ruri, is Sanskrit vaiḍūrya, a blue, translucent precious stone. What the sutra entrusts to this gem is not the luxury of jewels but a metaphor for purity, transparent inside and out, without a single cloud. The second vow promises "a body like lapis lazuli, luminous and transparent within and without," and teaches that its light surpasses even the sun and moon.

Four Chinese translations have come down to us.

Set side by side, these four translations show a scripture growing from a "one-buddha sutra" teaching a single Medicine Buddha into a "seven-buddha sutra." From the first translation to the fourth, roughly two hundred and fifty years passed. It is a scripture retranslated and read anew, its devotion deepening each time.

A medicine jar in the left hand, the right hand raised in the fear-dispelling gesture (semui-in). This form so familiar in Japan is, in fact, nowhere prescribed in the sutra.

It may come as a surprise, but the Bhaiṣajyaguru Sūtra does not define the Medicine Buddha's appearance. Even regarding image-making, Xuanzang's translation only urges, "one should first make an image of that buddha," and says nothing about what he holds in his hands.

What the sutra speaks of is not the shape of the body but its substance. The second great vow likens that body to lapis lazuli.

Where, then, did the medicine jar in the left hand come from? The oldest explicit textual source for a medicine vessel held in the hand is a passage in the Ritual Manual for the Recitation of the Medicine Master Tathāgata, transmitted as a translation by Amoghavajra: "Let the Tathāgata's left hand hold a medicine vessel. It is also called the priceless jewel" (Taishō Tripiṭaka No. 924A). The ritual handbooks (jisōsho, manuals recording the practical conduct of rites) of Japanese Shingon defined this jar as the Medicine Buddha's samaya form (sanmaya-gyō, the emblem that expresses a deity's fundamental vow) and transmitted as a secret teaching that it should be called "the jar of the twelve supreme vows" (Shoson yōshō). On this reading, what the jar contains is the Twelve Great Vows themselves. It should be added that Yakushi images without the medicine jar are by no means rare among older statues. More than the presence or absence of the emblem, the body that carries the vows is the true substance of this image.

The Medicine Buddha in the east for blessings in this life, Amida in the west for salvation in the next. The contrast is often drawn. The sutra itself declares the two pure lands equal.

The Medicine Buddha's land is the Pure Lapis Lazuli World in the far east. Xuanzang's translation describes its adornment as follows.

The Medicine Buddha in the east for present suffering, Amida in the west for the life to come. The division is easy to remember, and Japanese devotion has on the whole followed it. Yet the sutra's own words are larger. The two pure lands are "equal, without difference," and every one of the twelve vows closes with "until at last they realize unsurpassed awakening." To heal the present, and to lead toward the next life and toward awakening: the Medicine Buddha is the buddha who took on both. The same sutra also teaches that if a person who aspires to birth in the Western Pure Land but whose resolve remains unsettled hears the name of the Medicine Buddha, eight great bodhisattvas will come at the end of life to show the way. The buddha of the east becomes a companion on the road even for those bound for the pure land of the west.

The light of day and the light of night, and twelve martial guardians. Around the Medicine Buddha serves a family of light and protection.

Standing at either side of the Yakushi triad are the bodhisattvas Suryaprabha (Nikkō, Sunlight) and Candraprabha (Gakkō, Moonlight). In Xuanzang's translation their names are Nikkō Henjō and Gakkō Henjō, names that mean spreading the light of the sun-disc and the moon-disc everywhere. The sutra never calls these two "attendants." It presents them as the foremost (jōshu, the head) of the innumerable bodhisattvas of the Pure Lapis Lazuli World and as successors who uphold the Medicine Buddha's treasury of the true Dharma. In the oldest translation their names differ, and the two bodhisattvas, there called Sun-Radiance and Moon-Purity, are said to be "next in line to the buddha's place." The triad arrangement in sculpture was settled in later times on the basis of this scriptural teaching.

And guarding the perimeter of the hall are the Twelve Heavenly Generals (jūni shinshō). In the sutra they are twelve generals of the yakṣas. The Sanskrit text calls them mahāyakṣasenāpati, generals of the great yakṣa armies.

Continuing this vow, the generals teach that those who wish to escape illness and calamity should recite this sutra, knot their names into a five-colored cord, and untie the knots when the wish is fulfilled. The rite of the five-colored cord is a venerable one, present in the sutra's own words from the oldest translation onward. By contrast, the association of the Twelve Heavenly Generals with the twelve zodiac signs or the twelve hours of day and night is nowhere taught in the Bhaiṣajyaguru Sūtra itself. Statues crowned with the zodiac animals, and talk of guardian deities assigned by birth year, are developments of later times, above all in Japan. The ritual handbooks of Japanese Shingon also transmit an oral teaching that the Twelve Heavenly Generals embody the Twelve Great Vows themselves and protect people from the calamities of the twelve months and the twelve hours (Hishō kuketsu).

The exoteric reading says he is called the Medicine Master because he was a physician in a former life. The esoteric reading says he is Mahāvairocana entered into the samādhi of healing.

Why is he named the Medicine Master? The Shingon ritual handbook Hishō kuketsu sets two readings side by side. In the exoteric account, this buddha was born into a physician's family in the causal stage (in'ni, his past lives of practice as a bodhisattva) and attained buddhahood through the merit of dispensing medicine; hence the name. In the esoteric understanding, by contrast, it transmits that Mahāvairocana of the Womb Realm enters the samādhi (sanmaji, a state of profound meditation) of dispelling illness and extending life, gives rise to the Twelve Great Vows, and extinguishes the illnesses of all beings, and that this very figure is the Medicine Buddha (an oral transmission of Hōon-in).

This reading is visible in the form of the statues themselves. Upon the meditation mudrā that the Medicine Buddha forms, the hokkai jō-in, the gesture of Mahāvairocana's meditation with both hands overlapped, rests the medicine jar. It is read as the sign that Mahāvairocana's meditation has ripened into the activity of healing.

The absence of the Medicine Buddha's name from the mandalas of the Two Realms is explained by the same logic. Seated in the east of the mandala is Akṣobhya (Ashuku Nyorai). Where, then, is the Medicine Buddha? The ritual handbooks answer: when all deities are gathered into the Two Realms, they are gathered into Mahāvairocana at the center, and the Medicine Buddha too should be understood as contained in the central court. Whether the Medicine Buddha and Akṣobhya are the same deity or distinct ones has been debated within Shingon since early times, and oral transmissions survive on both sides, some holding them distinct and some identical. Esoteric Buddhism is a world of oral transmission, and it is not folded into a single answer.

It may be added that the rite of the Seven Buddhas of Healing, in which the seven buddhas are enshrined together, is consistently described in Shingon literature as a rite of the Tendai (Taimitsu) tradition; Shingon has performed the Yakushi rite with the single buddha.

The sutra teaches again and again that salvation is at work the moment the name passes once through the ear. To recite the mantra is to give that name a voice and to be joined with the one who made the vows. More than the count or the skill of recitation, please treasure reciting quietly and joining your hands in prayer.

Devotion to the Medicine Buddha in Japan is thought to have begun almost simultaneously with the arrival of Buddhism itself. Its gateway was not doctrine first, but medicine. The Nihon Shoki entry for the sixth year of Emperor Bidatsu (577) records that a jugonshi (a specialist who treated illness by incantation) arrived from Baekje together with scriptures and treatises. Scholarship infers that devotion to the Medicine Buddha crossed the sea as one body with the healing techniques of Buddhism.

From then on, from the prayers of the state to the daily life of the common people, the Medicine Buddha remained on the main stage of Japanese Buddhism.

• Bidatsu 6 (577). A jugonshi arrives from Baekje. The reception of Buddhist medicine is thought to have prepared the ground for devotion to the Medicine Buddha.
• Tenmu 9 (680). Emperor Tenmu vows the founding of Yakushiji in prayer for the recovery of his empress. This is the earliest record in which devotion to the Medicine Buddha can be firmly confirmed in the sources. The Yakushi image in the Golden Hall of Hōryūji is said to have been made for Emperor Yōmei, but the dating of the statue is disputed and it is not considered reliable evidence for the earliest transmission.
• The reign of Tenmu. Edicts pairing the release of living creatures (hōjō, the good act of freeing captured animals, encouraged by the Bhaiṣajyaguru Sūtra) with the nationwide great purification (ōharae) continued through this era, and the thought of the sutra intertwined with Japan's ancient practice of purification.
• Nara period. The Yakushi keka (a rite of repenting one's sins before the Medicine Buddha) was performed as a state ceremony, and temples such as Shin-Yakushiji were founded as halls for this rite of repentance.
• Nara to Heian. Yakushi images counted among the summits of Japanese sculpture were created one after another: the Yakushi triad of the Golden Hall of Yakushiji, the Yakushi Nyorai and Twelve Heavenly Generals of Shin-Yakushiji, and the standing Yakushi of Jingoji.
• The 8th of every month. The ennichi (feast day) of the Medicine Buddha. To this day, prayers on the 8th continue at Yakushi halls across the country.

The principal image of the Main Hall of Byodoji, the twenty-second temple of the Shikoku Eighty-Eight Sacred Sites, is Yakushi Nyorai. The temple's very name was born from this buddha's vow.

According to temple tradition, in the fifth year of Kōnin (814), as Kōbō Daishi was performing rites at this place, a Sanskrit syllable the color of lapis lazuli appeared out of light in the air before him, took the form of the Medicine Buddha, and radiated five-colored light. The Daishi received this sign as the vow "I heal and remove the sufferings of all beings equally, without distinction," carved the Medicine Buddha together with Suryaprabha and Candraprabha (Nikkō and Gakkō) and the Twelve Heavenly Generals in the manner of ittō sanrai (bowing three times with each stroke of the blade), and named the temple Byodoji, "the temple of equality." The principal image and his family of light were carved as one set from the very beginning.

The present principal image, a seated statue in joined-woodblock construction with lacquered gold leaf, is considered a second-generation image modeled on that first statue and completed in the Muromachi period. The medicine jar in the left hand alone, however, is made of metal; it is said to be more than a thousand years old and is surmised to have been inherited from the first image. The jar that the sutra never prescribed, and that esoteric Buddhism read as "the jar of the Twelve Great Vows," this statue has kept upon its hand, in actual fact, for a thousand years.

The temple bears two in-names: Iō-in and Nikkō-in. Iō-in derives from Iō Zenzei, an epithet of the Medicine Buddha. Nikkō-in comes from a tradition that on the morning of the founding, the sunlight reflected on the surface of the consecrated water was received as the form of the Eleven-Faced Kannon, an origin distinct from the bodhisattva Nikkō of the Yakushi triad. The mountain name Hakusui-zan, "Mountain of White Water," derives from the tradition that when the Daishi struck the rock with his single-pronged vajra, water as white as milk sprang forth. That water still rises within the temple grounds today as the "sacred water of Kōbō Daishi."

From the hand of the principal image, a five-colored cord stretches all the way to the temple gate, so that those who cannot climb the stone steps may touch the cord and form a bond with the principal image. It is the rite of the five-colored cord vowed by the Twelve Heavenly Generals in the Bhaiṣajyaguru Sūtra, alive in the temple grounds today. Three box-carts (hakoguruma) are also enshrined in the Main Hall, said to have been left behind in the Taishō era by pilgrims who could not walk, recovered in this hall, and departed on foot leaning on their pilgrim staffs.

On the night of the 8th of every month the Yakushi goma is performed, and goma is also performed every Sunday afternoon, continuing the prayers for the healing of body and mind, for sound legs and hips, for recovery from eye disease, and for protection against cancer. The links below explain how to attend and how to apply. You may also participate online.

The Bhaiṣajyaguru of Byodoji

• The Principal Image of Byodoji, Yakushi Nyorai (introduction)
• The Yakushi Goma on the 8th of Every Month (explanation and application)
• The Legend of the Box-Carts