Śatapatha Brāhmaṇa ("of a hundred paths") 6.3.1.7

6.3.1.7

yadvevaitāmāhutiṃ juhoti | savitaiṣo 'gnistametayāhutyā purastādreto bhūtaṃ siñcati yādṛguai yonau retaḥ sicyate tādṛgjāyate tadyadetayā savitāraṃ reto bhūtaṃ siñcati tasmātsāvitrāṇi tasmādvā etāmāhutiṃ juhoti

And, again, why he offers this libation;--this Agni is Savitri, and him he pours out as seed at the outset by this libation; and whatlike seed is poured into the womb suchlike (offspring) is born. And inasmuch as by this (libation) he pours out Savitri as seed, they (the offering-formulas are called) Sâvitra: that is why he offers this libation.