The Mantra of Light (光明真言, kōmyō shingon), also called the Mantra of the Unfailing Rope Snare, is an important mantra of the Shingon and Kegon sects of Buddhism, but is not emphasized in other Vajrayana sects of Buddhism. It is taken from the Amoghapāśakalparāja-sūtra (Chinese translation Taisho ed. no. 1092) or Sutra of the Mantra of the Unfailing Rope Snare of the Buddha Vairocana's Great Baptism and is chanted as follows:
The translation of this mantra, according to Professor Mark Unno, is roughly:
Praise be to the flawless, all-pervasive illumination of the great mudra [or seal of the Buddha ]. Turn over to me the jewel, lotus and radiant light.
Initially, the mantra received little mention in East Asian Buddhist texts, and although Kukai brought the sutra to Japan in the 9th century, there are no records that he ever utilized it in tantric practices. Records show gradually increasing use in the Heian Period, until the 13th century when it was popularized in medieval Japanese Buddhism by Myōe, and later by Shingon monks Eison and Ninshō in their ministries. Both the Mantra and the nembutsu were often incorporated by medieval Buddhists at one time or another, often in the same service. A common practice for the Mantra of Light was to sprinkle pure sand, blessed with this mantra, on the body of a deceased person or their tomb, based on teachings expounded in the Sutra. The belief was that a person who had accumulated much bad karma, and possible rebirth in Hell would be immediately freed and allowed a favorable rebirth into the Pure Land of Amitabha Buddha. This practice is known as dosha-kaji (土砂加持) in Japanese.