Śatapatha Brāhmaṇa ("of a hundred paths") 6.2.2.15

6.2.2.15

yadvevaitam paśumālabhate | etasminha paśau sarveṣām paśūnāṃ rūpaṃ yattūparo lapsudī tatpuruṣasya rūpaṃ tūparo hi lapsudī puruṣo yattūparaḥ kesaravāṃstadaśvasya rūpaṃ tūparo hi kesaravānaśvo yadaṣṭāśaphastadgo rūpamaṣṭāśapho hi gauratha yadasyāveriva śaphāstadave rūpaṃ yadajastadajasya tadyadetamālabhate tena haivāsyaite sarve paśava ālabdhā bhavantyato yatamadasya karmopakalpetaite vā pañca paśava eṣa vā prājāpatya eṣa vā niyutvatīyaḥ

And, again, why he slaughters this animal;--in this animal doubtless the form of all (the five kinds of) animals is (contained): inasmuch as it is hornless and bearded, that is the form of man, for man is hornless and bearded; inasmuch as it is hornless and furnished with a mane, that is the form of the horse, for the horse is hornless and furnished with a mane; inasmuch as it is eight-hoofed, that is the bull's form, for the bull is eight-hoofed; inasmuch as its hoofs are like those of the sheep, that is the form of the sheep; and inasmuch as it is a he-goat, that is that of the goat. Thus when he slaughters this one, thereby indeed all those (five) animals are slaughtered for him. Whichever of these may suit him--either those five animals, or that (he-goat) for Pragâpati, or that one for (Vâyu) Niyutvat --