SB 9.1.15

preṣito ’dhvaryuṇā hotā
 vyacarat tat samāhitaḥ
gṛhīte haviṣi vācā
 vaṣaṭ-kāraṁ gṛṇan dvijaḥ
Word for word: 
preṣitaḥ — being told to execute the sacrifice; adhvaryuṇā — by the ṛtvik priest; hotā — the priest in charge of offering oblations; vyacarat — executed; tat — that (sacrifice); samāhitaḥ — with great attention; gṛhīte haviṣi — upon taking the clarified butter for the first oblation; vācā — by chanting the mantra; vaṣaṭ-kāram — the mantra beginning with the word vaṣaṭ; gṛṇan — reciting; dvijaḥ — the brāhmaṇa.
Translation: 
Told by the chief priest “Now offer oblations,” the person in charge of oblations took clarified butter to offer. He then remembered the request of Manu’s wife and performed the sacrifice while chanting the word “vaṣaṭ.”