Hiranyakeshigrihyasutra 1.7.25.2

1.7.25.2

bhūḥ prajāpatinātyṛṣabheṇa skandayāmi vīraṃ dhatsvāsau bhuvaḥ prajāpatinātyṛṣabheṇa skandayāmi vīraṃ dhatsvāsau suvaḥ prajāpatinātyṛṣabheṇa skandayāmi vīraṃ dhatsvāsau iti vīraṃ haiva janayati \2\

(He should cohabit with her with the formulas), 'Bhûh! Through Pragâpati, the highest bull, I pour forth (the sperm); conceive a valiant son, N.N.! Bhuvah! Through Pragâpati, &c.—Suvah! Through Pragâpati, &c.' Thus he will gain a valiant son.