Solomon
Proverbs 20:5BSB·traditional attribution

The intentions of a man’s heart are deep waters, but a man of understanding draws them out.

Matthew Henry Presbyterian

A man's wisdom is here said to be of use to him for the pumping of other people, and diving into them, 1. To get the knowledge of them. Though men's counsels and designs are ever so carefully concealed by them, so that they are as deep water which one cannot fathom, yet there are those who by sly insinuations, and questions that seem foreign...

John Gill Reformed Baptist

Counsel in the heart of man is like deep water,.... Pure and undisturbed, but secret, hidden, and hard to be come at: such are the things of the spirit of a man, the thoughts of his mind, the devices of his heart; which, though easily known by the searcher of hearts, are not easily penetrated into by men; or it is not easily got out...

Jamieson-Fausset-Brown Reformed

Counsel . . . water--that is, deeply hidden (Pro 18:4; Psa 13:2). The wise can discern well.