Shatapatha Brahmana 1.7.1.17

1.7.1.17

athāha kāmadhukṣa iti amūmiti sā viśvāyurityatha dvitīyām pṛcati kāmadhukṣa ityamūmiti sā viśvakarmetyatha tṛtīyām pṛcati kāmadhukṣa ityamūmiti sā viśvadhāyā iti tadyatpṛcati vīryāṇyevāsvetaddadhāti tisro dogdhi trayo vā ime lokā ebhya evainadetallokebhyaḥ sambharatyatha kāmaṃ vadati

He then says (Vâg. S. I, 3-4), 'Which didst thou milk?' 'Such and such a one,' (the milker replies.) 'This one is Visvâyu (containing all life),' he (the Adhvaryu) says. He then asks regarding the second one, 'Which didst thou milk?' 'Such and such a one,' is the reply. 'This one is Visvakarman (all-doing),' he says. He then asks regarding the third, 'Which didst thou milk?' 'Such and such a one,' is the reply. 'This one is Visvadhâyas (all-sustaining),' he says. The reason why he thus asks is that he thereby bestows certain energies on them. Three (cows) he milks, for three are these worlds: he thereby renders them fit for these worlds. He is now at liberty to speak.