Yāska's Nirukta 189.2.5

189.2.5

4 )-indrārthaṃ somaḥ saṃskriyate, tasmādindra evāsya kevalaḥ pātā, nānya iti| naitadevam, somo hyanyasyai devatāyai mīyate, anyasyai saṃskriyate, anyābhyaśca gṛhyate, hūyate ca | tadyathā “a̱bhi tyaṃ de̱vam”-iti sāvitryā'tyaṣṭyāmīyate, “aṃśu̱raṃśu̱ṣṭe”-iti indrāya saṃskriyate, punarapi ca mīyate “indrāyatvābhimātighne”-ityevamādibhiḥ| nānādevatābhyo gṛhyate ca maitrāvaruṇādyābhyaḥ| tathā ca hūyate | tadevaṃ vidhivaśāt vicitrā somatantragatiḥ| tatraivaṃ satyaśakyaṃ vaktuṃ yatra yatra somaḥ, tatra tatrendraḥ pātā iti | sambhaikte cāgnirindreṇa saha pratyakṣamaindrāgne grahe “indrā̍gnī ārga̍tam”-ityatra | bhavati cānyarthamapi pṛthak grahaṇaṃ yajuṣā somasya “agnaye tvā rāyaspoṣāya tvā”-iti || tasmādagnirapi somasya pātā syāt |