The tradition of the Vedic ritual was handed down in two forms. The one class, called Çrauta Sutras, because based on çruti or revelation (by which in this case the Brahmanas are chiefly meant), deal with the ritual of the greater sacrifices, for the performance of which three or more sacred fires, as well as the ministrations of priests, are necessary. Not one of them presents a complete picture of the sacrifice, because each of them, like the Brahmanas, describes only the duties of one or other of the three kinds of priests attached to the respective Vedas. In order to obtain a full description of each ritual ceremony, it is therefore needful to supplement the account given by one Çrauta Sutra from that furnished by the rest. The other division of the ritual Sutras is based on smriti or tradition. These are the Grihya Sutras, or "House Aphorisms," which deal with the household ceremonies, or the rites to be performed with the domestic fire in daily life. As a rule, these rites are not performed by a priest, but by the householder himself in company with his wife. For this reason there is, apart from deviations in arrangement and expression, omission or addition, no essential difference between the various Grihya Sutras, except that the verses to be repeated which they contain are taken from the Veda to which they belong. Each Grihya Sutra, besides being attached to and referring to the Çrauta Sutra of the same school, presupposes a knowledge of it. But though thus connected, the two do not form a unity. The second class of Sutras, which deal with social and legal usage, is, like the Grihya Sutras, also based on smriti or tradition. These are the Dharma Sutras, which are in general the oldest sources of Indian law. As is implied by the term dharma, "religion and morality," their point of view is chiefly a religious one. They are closely connected with the Veda, which they quote, and which the later law-books regard as the first and highest source of dharma.