YV 5.6h

In that he mixes (the cup) for (Tvastr) with the wives with ghee, he overpowers it with a bolt and draws it. 'Thou art taken with a support', he says; the support is this (earth); therefore offspring are born on this (earth). 'Of thee, pressed by Brhaspati ', he says; Brhaspati is the holy power of the gods; verily by the holy power he produces offspring for him. 'O drop', he says; the drop is seed; verily thus he impregnates seed. 'Possessing power', he says [3]; power is offspring; verily he produces offspring for him. 'O Agni', he says; the impregnator of seed is Agni; 'With the wives', he says, for pairing; 'in unison with the god Tvastr drink the Soma', he says; Tvastr is the maker of the forms of pairings of animals; verily he places form in animals. The gods sought to slay Tvastr; he went to the wives, they would not give him up; therefore [4] men do not give up even one worthy of death who has come for help. Therefore in (the cup) for the wives for Tvastr also a drawing is made. He does not put (the cup) down, for from what is not depressed offspring are produced. He does not utter the secondary Vasat; if he were to do so, he would let Rudra go after his offspring; if he were not to do so, the Agnidh would consume the Soma before it had been appeased; he says the secondary Vasat muttering, he does not let Rudra go after his offspring, the Agnidh consumes the Soma after it has been appeased. 'O Agnidh, sit on the lap of the Nestr; O Nestr, lead up the wife', he says verily the Agnidh impregnates the Nestr, the Nestr the wife. He causes the Udgatr to look (at the wife); the Udgatr is Prajapati; (verily it serves) for the production of offspring. He causes water to follow along; verily thus he pours seed; along the thigh he causes it to flow, for along the thigh is seed poured; baring the thigh he causes it to flow, for when the thigh is bared, they pair, then seed is poured, then offspring are born.