Śatapatha Brāhmaṇa ("of a hundred paths") 2.2.2.14

2.2.2.14

athainaṃ devāḥ | antarātmannādadhata ta imamamṛtamantarātmannādhāyāmṛtā bhūtvāstaryām bhūtvā staryāntsapatnānmartyānabhyabhavaṃstatho evaiṣa etadamṛtamantarātmannādhatte nāmṛtatvasyāśāsti sarvamāyuretyastaryo haiva bhavati na hainaṃ sapatnastustūrṣamāṇaścana stṛṇute tasmādyadāhitāgniścānāhitāgniśca spardhete 'āhitāgnirevābhibhavatyastaryo hi khalu sa tarhi bhavatyamṛtaḥ

The gods then established that (fire) in their innermost soul; and having established that immortal element in their innermost soul, and become immortal and unconquerable, they overcame their mortal, conquerable enemies. And so this one now establishes that immortal element in his innermost soul; and--though there is for him no hope of immortality--he obtains the full measure of life; for, indeed, he becomes unconquerable, and his enemy, though striving to conquer, conquers him not. And, accordingly, when one who has established his fires and one who has not established his fires, vie with each other, he who has established his fires overcomes the other, for, verily, he thereby becomes unconquerable, he thereby becomes immortal.