The Vedanta Sutras of Badarayana, Commentary by Sankara (SBE38), tr. by George Thibaut  at sacred-texts.com
31. And hence also a scriptural passage as to non-proceeding according to liking.
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 Samhitâ of the Kathas, 'Therefore a Brâhmana is not to drink spirits.' This text also is more appropriate if we take the passage, 'To him who knows this,' as an arthavâda.--Hence passages of that kind are arthavâdas, not injunctions.