Trayi is the name of the three Vedas together. Rig Veda, Yajur Veda and Sama Veda are collectively referred to as trayi in Satapatha Brahmana. It is used in the same sense in the enumeration of the lore in the ethics of Kamandaka and in the lexicon of Amarasimha.
Rig Veda has hymns glorifying the Vedic gods for the prosperity of the people, Yajur Veda supplies the details relating to the sacrifices and Sama Veda contains hymns mostly culled from Rig Veda to be sung in order to praise the gods and manes.
Since the three Vedas are recognized as important in the performance of the srauta (Vedic0 and grihya (domestic rituals), Atharva Veda, consisting of hymns of nourishment and appeasement, and taken from Rig Veda, stands separate.
Brahmais said to have milked the three Vedas from the three gods – Fire, Wind and Sun – to accomplish the rituals. The syllable om is said to be the essence the trayi. The priest has to learn the trayi and other lore from those who have mastered the three Vedas. The trayi is recognized as conferring, on the devout who have studied them, seen and unseen benefits. The Sun God is glorified as an embodiment the three Vedas (Trayimaya). There is no other dharma than that laid down in the three Vedas, i.e., trayidharma. Chanting of the three Vedas is said to wash away the sins arising from minor offences.