Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 14: The Aśvamedha Sacrifice
Text 1.14.4

प्रवर्ग्यं शास्त्रतः कृत्वा तथैवोपसदं द्विजाः।
चक्रुश्च विधिवत्सर्वमधिकं कर्म शास्त्रतः॥

pravargyaṁ śāstrataḥ kṛtvā tathaivopasadaṁ dvijāḥ
cakruś
ca vidhivat sarvam adhikaṁ karma śāstrataḥ

pravargyam = the pravargya ritual; śāstrataḥ = according to the scriptures; kṛtvā = performed and; tathā eva = then; upasadam = performed the upasada ritual; dvijāḥ = the sacrificial priests; cakruḥ ca = they then performed; vidhivat = in accordance with the rules and regulations; sarvam = all; adhikam = further; karma = of the rituals; śāstrataḥ = based on the scriptures that prescribe procedures for sacrificial rituals.

The sacrificial priests performed the pravargya ritual according to the scriptures, and then in accordance with the rules and regulations performed the upasada ritual. They then performed further all of the rituals based on the scriptures that prescribe procedures for sacrificial rituals.

After procuring soma, they performed the Soma-rājāpyayana, a special ritual. Pravargya refers to a specific ritual described in the Pravargya Brāhmaṇa of the Taittirīya Āraṇyaka. The sacrificial priests performed this ritual and the Upasada ritual (a specific Iṣṭi performance) taking into consideration the rules, the principles of Mīmāṁsā and the injunctions of the Kalpa-sūtras. They performed twelve Pravargya and Upasada rituals [4].

[4] tisra eva sāhnasyopasado dvādaśāhīnasya.