Śatapatha Brāhmaṇa ("of a hundred paths") 11.3.3.2

11.3.3.2

dīrghasattraṃ vā eṣa upaiti yo brahmacaryamupaiti sa yāmupayantsamidhamādadhāti sā prāyaṇīyā yāṃ snāsyantsodayanīyātha yā antareṇa sattryā evāsya tā brāhmaṇo brahmacaryamupayan

He who enters on a Brahmakârin's life, indeed, enters on a long sacrificial session: the log he puts on the fire in entering thereon is the opening (offering), and that which (he puts on the fire) when he is about to bathe is the concluding (offering); and what (logs) there are between these, are just his (logs) of the sacrificial session. When a Brâhmana enters on a Brahmakârin's life--