Śaṅkaraon Brahma Sūtra 3.4.41
Advaita Vedānta
Sūtra
न चाऽऽधिकारिकमपि पतनानुमानात्तदयोगात्
na cā''dhikārikamapi patanānumānāttadayogāt
Sūtra translation
And not also (can the expiation take place) prescribed in the chapter treating of qualification, because on account of the inference of his lapse from SmrAi he (the Naish//dka) is not capable of it.
If a BrahmaHrin for life breaks from inattention the vow of chastity, is he to perform the expiatory sacrifice enjoined by the text, ‘ A student who has broken the vow of chastity shall sacrifice an ass to Nir/iti^’ or not?—He is not, the purvapakshin says. For although in the chapter which treats of qualification (Pu. Mim. Sii. VI, 8, 22) that expiatory ceremony has been settled (for Brahma/tarins in general), it does not yet hold good for the professed Brahma/tarin. For Smr/ti declares that such sins cannot be expiated by him any more than a head once cut off can again be healed on to the body, ‘He who having once entered on the duties of a Naish^f/zika again lapses from them, for him—a slayer of the Self—I see no expiation which might make him clean again.’ The Upakurvawa (i. e. he who is a Brahma^’firin for a certain time only, not for life) on the other hand, about whose sin Smrfti makes no similar declaration, may purify himself by the ceremony mentioned.