Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 60: Triśaṅku Blessed
Text 1.60.8

एवमुक्त्वा महर्षयः चक्रुस्तास्ताः क्रियास्तदा।
याजकश्च महातेजा विश्वामित्रोऽभवत्क्रतौ॥

evam uktvā maha-rṣayaḥ cakrus tās tāḥ kriyās tadā
yājakaś
ca mahā-tejā viśvāmitro ‘bhavat kratau

evam uktvā = having said this; mahā-ṛṣayaḥ = the great sages; cakruḥ tāḥ tāḥ kriyāḥ = performed their respective duties as sacrificial priests; tadā = then; yājakaḥ ca = the adhvaryu priest; mahā-tejāḥ = of great prowess; viśvāmitraḥ = Viśvāmitra; abhavat = acted as; kratau = in that sacrifice.

Having said this, the great sages then performed their respective duties as sacrificial priests. In that sacrifice, Viśvāmitra of great prowess acted as the adhvaryu priest.

It is understood that Viśvāmitra acted as the adhvaryu priest, for it will be mentioned later on that he used the sruva [and spoke to Triśaṅku].