Śatapatha Brāhmaṇa ("of a hundred paths") 6.3.1.6

6.3.1.6

yadvevaitāmāhutiṃ juhoti | savitaiṣo 'gnistametayāhutyā purastātprīṇāti tamiṣṭvā prītvāthainaṃ sambharati tadyadetayā savitāram prīṇāti tasmāsāvitrāṇi tasmādvā etāmāhutiṃ juhoti

And, again, why he offers that libation;--this Agni is Savitri, and him he gratifies at the outset by this libation; and having sacrificed to, and gratified, him (Agni), he then puts him together. And inasmuch as by this (libation) he gratifies Savitri, they (the formulas are called) Sâvitra: that is why he offers this libation.