Śaṅkaraon Brahma Sūtra 3.4.31

There is also a scriptural passage prohibiting unlawful food, the purpose of which it is to stop procedure therein according to one’s liking, viz. in the Sawhit^ of the Ka//^as, ‘ Therefore a Brcihma;/a is not to drink spirits.’ This text also is more appropriate if we take the passage, ‘To him who knows this,’ as an arthavada.—Hence passages of that kind are arthavAdas, not injunctions.