Solomon
Proverbs 25:18ESV·traditional attribution

A man who bears false witness against his neighbor is like a war club, or a sword, or a sharp arrow.

Matthew Henry Presbyterian @wholebiblehenry

Here, 1. The sin condemned is bearing false witness against our neighbour, either in judgment or in common conversation, contrary to the law of the ninth commandment. 2. That which it is here condemned for is the mischievousness of it; it is in its power to ruin not only men's reputation, but their lives, estates, families, all that is dear to them.

John Gill Reformed Baptist @doctorgill

A man that beareth false witness against his neighbour,.... In whose house he has often been, and whom he has frequently visited; and, observing what was done there, not only discovers and tells abroad the secrets of his family, but even things which are false; yea, in a court of judicature, appears a witness against him, and swears falsely to his hurt and prejudice.

Jamieson-Fausset-Brown Reformed @jfbcommentary

A false witness is as destructive to reputation, as such weapons to the body (Pro 24:28). beareth . . . witness--literally, "answereth questions," as before a judge, against his neighbor.