Śatapatha Brāhmaṇa ("of a hundred paths") 2.2.1.4

2.2.1.4

yāṃ vai prajāpatiḥ | prathamāmāhutimajuhotsvāheti vai tāmajuhotso svideṣā nidānena tasmātsvāheti juhoti tasyāṃ varaṃ dadāti sarvaṃ vai varaḥ sarveṇaivainametacamayati

The first offering which Pragâpati made, he made with 'Svâhâ!' Now that (offering) indeed is virtually the same as this one; and hence he (the sacrificer) also makes it with 'Svâhâ!' At this (offering) he grants a boon (to the priests); but a boon (may mean) everything, so that he thereby appeases him (Agni) with everything.