Mbh 12.346.2a

"'Narada said, "Thou saidst unto me on a former occasion that rites and observances in honour of the deities should be accomplished. Thou saidst that the rites in honour of the deities constitute the highest sacrifice and are equivalent to the worship of the eternal Supreme Soul. Instructed by that teaching, I always sacrifice in honour of the eternal and immutable Vishnu, through these rites that I perform in worshipping the deities. It is from that Supreme Deity that Brahma, the Grandsire of all the worlds, took his rise in days of yore. That Brahma, otherwise called Prameshthi, filled with cheerfulness, caused my sire (Daksha) to start into being. I was the son of Brahma, created before all others, by a fiat of his will (although I had to take birth afterwards as the son of Daksha through a curse of that Rishi). O righteous and illustrious one, I am performing these rites in honour of the Pitris for the sake of Narayana, and agreeable to those ordinances that have been laid down by himself. The illustrious Narayana is the father, mother, and grandfather (of all creatures). In all sacrifices performed in honour of the Pitris, it is that Lord of the universe who is adored and worshipped. On one occasion, the deities, who were sires, taught their children the Srutis. Having lost their knowledge of the Srutis, the sires had to acquire it again from those sons unto whom they had communicated it. In consequence of this incident, the sons, who had thus to communicate the Mantras unto their sires, acquired the status of sires (and the sire, for having obtained the Mantras from their sons, acquired the status of sons).[1891] Without doubt, what the deities did on that occasion is well known to you two. Sons and sires (on that occasion) had thus to worship each other. Having first spread some blades of Kusa grass, the deities and the Pitris (who were their children) placed three Pindas thereon and in this way worshipped each other.