YV 5.6i

Indra slew Vrtra; he forced out his skull-bone, it became the wooden tub, from it the Soma flowed, it became (the cup) for the yoker of bays; he reflected regarding it, 'Shall I offer, or shall I not offer?' He reflected, 'If I shall offer, I shall offer what is raw; if I shall not offer, I shall make confusion in the sacrifice.' He decided to offer; Agni said, Thou shalt not offer what is raw in me'; he mixed it with fried grains [1], and when it had become cooked he offered it. In that he mixes (the cup) for the yoker of bays with fried grains, (it serves) to make it cooked; verily he offers it when it has become cooked. He mixes with many; so many are his (cows) yielding his wishes in yonder world. Or rather they say,'(The fried grains) for the yoker of bays are the dappled (cows) of Indra yielding wishes'; therefore he should mix with many. The bays of Indra, which drink the Soma, are the Rc and the Saman, the enclosing-sticks are their bridles; if he should offer without removing the enclosing-sticks, he would offer fodder to them still bridled [2]; he offers after removing the enclosing-sticks; verily he offers fodder to them with their bridles removed. It is the Unnetr who offers; the Adhvaryu when he has uttered 'Godspeed!' is as one who has finished his journey; if the Adhvaryu were to offer, it would be as when one yokes again (a horse) unyoked. He offers after putting it on his head, for from the head it sprung; he offers after striding, for Indra slew Vrtra after striding; (verily it serves) for attainment. (The grains) for the yoker of bays are cattle; if he were to crush (them), few [3] cattle would attend and wait on him; if he were not to crush them, many cattle would attend, but not wait on him; in his mind he crushes them together, and effects both; many cattle attend and wait on him. They await the invitation from the Unnetr; verily they win the Soma- drinking that is here.