Agni Purana 64.20

64.20

vedādimantrair gandhādyāś catasro dhenavo duhet /
dikṣvatho vai yavacaruṃ tataḥ saṃsthāpya homayet(2) //

he should milk four cows endowed with perfumes and other offerings with the mantras beginning with the Vedas;
and then, placing barley caru in the directions, he should make fire oblations;