Jaiminīya (Talavakāra) Brāhmaṇa 1.38

He should offer that fire-offering for three days with milk alone;
that is the form of the Agniṣṭoma.
It is as if he has sacrificed with the Agniṣṭoma, for him who, knowing thus, offers the fire-offering.
He should offer that fire-offering for three days with sour milk alone;
that is the form of the Vājapeya.
It is as if he has sacrificed with the Vājapeya, for him who, knowing thus, offers the fire-offering.
He should offer that fire-offering for three days with clarified butter alone;
that is the form of the Aśvamedha.
It is as if he has sacrificed with the Aśvamedha, for him who, knowing thus, offers the fire-offering.
He should offer that fire-offering for three days with water alone;
that is the form of the Puruṣamedha.
It is as if he has sacrificed with the Puruṣamedha, for him who, knowing thus, offers the fire-offering.
Not staying away [from home], the sacrificer should himself offer the fire-offering wearing unwashed garments, in the perpetual fires.
On the thirteenth night, having sacrificed either with soma or with an animal, he should let [it] go;
it is just as if one were to set free [cattle] having made an abode for them.
The earlier men offered that fire-offering for twelve days alone.
Therefore for them the milch cow yields milk, the draft-ox pulls, the horse set forth with a burden or the mule waits upon [them], the elephant with girth-bands carries.

He says: 'Having let loose the agnihotra cow'; heaven and earth are let loose.

'The Rudras receive the milk of the Vasus.'

'You are the makers of beings; removed is the fear born of folk'—with this he pushes out the burning coals.