Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 18.1.3

18.1.3

bhrātṛvyas tena yajamānasya pratyudyamī bhavati / (soma: aAśvina śastra)

xviii. 1. The Āçvina (Çastra) is (a sacrifice) wherein there is a redundancy of Soma; wherein in the sacrifice there is a redundancy, thereby the rival of the sacrificer is energetic against him. In that afterwards he sacrifices to the Açvins, and the Açvins are the physicians of the gods, verily thus he makes medicine. Now when Savitṛ gave Sūryā to Soma, the king, he made over to his daughter whether she was Prajāpati's (or his own) on