Śatapatha Brāhmaṇa ("of a hundred paths") 4.4.4.4

4.4.4.4

atha yasmātsamiṣṭayajūṃṣi juhoti | riricāna iva vā etadījānasyātmā bhavati yaddhyasya bhavati tasya hi dadāti tamevātastribhiḥ punarāpyāyayati

And as to why he offers the Samishtayagus. Now, the self of him who has sacrificed has, as it were, become emptied, since he gives away of whatever is his: it is him he fills again by three out of these (oblations).