Śatapatha Brāhmaṇa ("of a hundred paths") 11.4.4.6

11.4.4.6

atha yo lohitena haviṣā yajate vidyutā ha sa brahmaṇo dvāreṇa pratipadyate sa vidyutā brahmaṇo dvāreṇa pratipa

And he who offers with browned sacrificial food, enters through the lightning-door of the Brahman, and, by entering through the lightning-door of the Brahman, he wins his union with, and participation in the world of, the Brahman.