Śatapatha Brāhmaṇa ("of a hundred paths") 2.2.3.23

2.2.3.23

tānyu hāgnirnicakame | taiḥ saṃgṛhya 'rtūnpraviveśa punarema iti devā edagniṃ tirobhūtaṃ teṣāṃ heyasevāsa kimiha kartavyaṃ keha prajñeti vā

If, on the other hand, they determine upon (offering to) Agni Indumat, let him say, 'Pronounce the invitatory prayer to Agni Indumat!' He (the Hotri) recites (Rig-veda VI, 16, 16), 'Come hither, I will gladly sing to thee yet other songs, O Agni! mayest thou grow strong by these draughts (indu, drop).' Thus, indeed, it becomes of the nature of Agni: the draught doubtless means Soma, but this (Soma-element) they eliminate from the butter-portion of Soma. For the offering-prayer he recites, 'May Agni, the drop-abounding, graciously accept of the butter!' And thus he makes it all of the nature of Agni.