Shatapatha Brahmana 1.9.2.27

1.9.2.27

atha yasmātsamiṣṭayajurjuhoti | yā vā etena yajñena devatā hvayati yābhya eṣa yajñastāyata upa ha vai tā āsate yāvanna samiṣṭayajurjuhvatīdaṃ nu no juhvatviti tā evaitadyathāyathaṃ vyavasṛjati yatra yatrāsāṃ caraṇaṃ tadanu yajñaṃ vā etadajījanata yadenamatata taṃ janayitvā yatrāsya pratiṣṭhā tatpratiṣṭhāpayati tasmātsamiṣṭayajurjuhoti

And again as to why he performs the samishtayagus: whatever deities he invites through this sacrifice, and for whichever deities this sacrifice is performed, they continue waiting until the samishtayagus is performed, thinking, 'This he must offer to us!' These same (deities) he thereby dismisses in due form; and whatever be the practice in their case in accordance with that he has, in thus performing it, produced the sacrifice, and having thus produced it he now establishes it safely where there is a safe basis for it: this is why he performs the samishtayagus.