Who is addressed as “the step of Vishnu” in the Yajur Veda?

Question

The Fourth Khanda of the Taittirya Samhita of the Yajur Veda is chanted during the preparation of the altar of a Yagna (fire-ritual), and the second Prapathaka of this Khanda, which is chanted during the preparation of the ground of the Yagna, begins with this hymn:

Thou art the step of Visnu, overcoming hostility, mount the Gayatri metre, step along the earth, excluded is he whom we hate. Thou art the step of Visnu, overcoming [curses], mount the Tristubh metre, step along the atmosphere, excluded is he whom we hate. Thou art the step of Visnu, overcomer of the enemy, mount the Jagati metre, step along the sky, excluded is he whom we hate. Thou art the step of Visnu, overcomer of the foe, mount the Anustubh metre, step along the quarters, excluded is he whom we hate.

Clearly "step of Vishnu" is a reference to Vishnu's incarnation (avataram) as Vamana the dwarf, who conquered the three worlds from the Asura (demon) Mahabali by taking three steps.

But my question is, who is the figure being addressed when the hymn says "Thou art the step of Vishnu"? The second Prapathaka is related to the preparation of the ground for the ritual, so could this be a hymn to the Earth, which is one of the places Vishnu that stepped on? Or is it referring to someone else?

Answer 1

I found the answer on page 368 of the book "The Dharmasutras: The Law Codes of Ancient India" by Patrick Olivelle:

Vishnu steps are the four steps a person offering the [Soma] sacrifice takes at its conclusion. He recites a ritual formula at each step, and every formula begins with "You are the step of Vishnu".

So when the Yajur Veda says "thou art the step of Vishnu", it's not addressing some god as I assumed. Rather, the performer of the Soma Yagna is addressing his own footsteps, which are supposed to symbolize the steps that Vishnu took in his Vamana incarnation.

I suppose the idea is roughly as follows. Mandala 7 of Rig Veda says this:

Over this earth with mighty step strode Viṣṇu, ready to give it for a home to Manu. In him the humble people trust for safety: he, nobly born, hath made them spacious dwellings.

So presumably just as the steps of Vishnu made the Earth safe for humanity, the performer of the Soma Yagna is supposed to take four ritualistic steps in order to make the ground safe for the completion of the ritual.