Śatapatha Brāhmaṇa ("of a hundred paths") 11.2.2

He recites a gâyatrî invitatory formula: the gâyatrî consisting of three feet, these worlds being three in number, it is these worlds the gods thereby established.

He offers with a trishtubh (verse): the trishtubh consisting of four feet, and cattle being four-footed, it is cattle the gods thereby established in these established worlds.

The Vashat-call consists of two syllables (vaushat): man being two-footed; it is two-footed man they thereby established among the established cattle.

Two-footed man, then, is established here among cattle. In like manner this (Sacrificer) establishes thereby the worlds; and in the established worlds he establishes cattle, and among the established cattle he establishes himself: thus, indeed, is that man established among cattle, who, knowing this, offers sacrifice.

And when he offers, after the Vashat has been uttered,--that Vashat-call being yonder shining (sun), and he being the same as Death --he thereby consecrates him (the Sacrificer) after death, and causes him to be born from out of it, and he is delivered from that death. And the sacrifice, indeed, becomes his body: thus, having become the sacrifice, he is delivered from that death, and all his chief offerings are thereby delivered from that death.

And, verily, whatever offering he there performs, that offering becomes his body in yonder world; and when he who knows this departs this world then that offering, being behind him, calls out to him, 'Come hither, here I am, thy body;' and inasmuch as it calls out (invokes, âhvayati), it is called 'âhuti' (offering or invocation).