John Gill, on Prov 23:2

And put a knife to thy throat,.... Refrain from too much talk at the table; give not too loose to thy tongue, but bridle it, considering in whose presence thou art; do not use too much freedom, either with the ruler or fellow guests; which, when persons have ate and drank well, they are too apt to do, and sometimes say things offensive to one or the other; it is good for a man to be upon his guard; see Ecc 5:2. Or restrain thine appetite; deny thyself of some things agreeable, that would lead thee to what might be hurtful, at least if indulged to excess: put as it were a knife unto thine appetite, and mortify it; which is the same as cutting off a right hand, or plucking out a right eye Mat 5:29. Or while thou art at such a table, at such a sumptuous entertainment, consider thyself as in danger, as if thou hadst a knife at thy throat; and shouldest thou be too free with the food or liquor, it would be as it were cutting thine own throat; if thou be a man given to appetite; there is then the more danger; and therefore such a person should be doubly on his guard, since he is in the way of temptation to that he is naturally inclined to. Or, "if thou art master of appetite" (r): so the Targum, "if thou art master of thy soul;'' if thou hast power over it, and the command of it, and canst restrain it with ease; to which agrees the Vulgate Latin version: but the former sense is more agreeable to the Hebrew idiom. (r) "dominus animae", Vatablus, Mercerus, Michaelis.