Shatapatha Brahmana 1.8.2.16

1.8.2.16

atha yadvasuvane vasudheyasyeti yajati | agnirvai vasuvanirindro vasudheyo 'sti vai candasāṃ devatendrāgnī evaivamu haitaddevatāyā eva vaṣaṭkriyate devatāyai hūyate

The reason, then, why he offers with the formula 'for abundant obtainment of abundant gift,' is that Agni is the obtainer of wealth, and Indra is the recipient of wealth; and Indra and Agni are indeed the (joint) divinity of the metres: and in this way it is for a deity that the vashat is pronounced, and to a deity that the offering is made.