Matthew Henry, on Prov 16:23

“The heart of the wise shall instruct his mouth: and shall add grace to his lips.”

“Solomon had commended eloquence, or the sweetness of the lips (Pro 16:21), and seemed to prefer it before wisdom; but here he corrects himself, as it were, and shows that unless there be a good treasure within to support the eloquence it is worth little. Wisdom in the heart is the main matter. 1. It is this that directs us in speaking, that teaches the mouth what to speak, and when, and how, so that what is spoken may be proper, and pertinent, and seasonable; otherwise, though the language be ever so fine, it had better be unsaid. 2. It is this that gives weight to what we speak and adds learning to it, strength of reason and force of argument, without which, let a thing be ever so well worded, it will be rejected, when it comes to be considered, as trifling. Quaint expressions please the ear, and humour the fancy, but it is learning in the lips that must convince the judgment, and sway that, to which wisdom in the heart is necessary.”

Imported from an open dataset — not yet checked against the printed edition.