Solomon
Ecclesiastes 5:6ESV·traditional attribution

Let not your mouth lead you into sin, and do not say before the messenger that it was a mistake. Why should God be angry at your voice and destroy the work of your hands?

Matthew Henry Presbyterian @wholebiblehenry

Four things we are exhorted to in these verses: - I. To be conscientious in paying our vows. 1. A vow is a bond upon the soul (Num 30:2), by which we solemnly oblige ourselves, not only, in general, to do that which we are already bound to do, but, in some particular instances, to do that to do which we were not under any...

Commenting on Ecclesiastes 5:4-8

John Gill Reformed Baptist @doctorgill

Suffer not thy mouth to cause thy flesh to sin,.... That is, himself, who is corrupt and depraved; either by making a rash vow, which it is not in his power to keep; or such is the corruption of his nature, and the weakness of the flesh, that he cannot keep it; or by making sinful excuses after he has made the vow, and so...

Jamieson-Fausset-Brown Reformed @jfbcommentary

thy flesh--Vow not with "thy mouth" a vow (for example, fasting), which the lusts of the flesh ("body," Ecc 2:3, Margin) may tempt thee to break (Pro 20:25). angel--the "messenger" of God (Job 33:23); minister (Rev 1:20); that is, the priest (Mal 2:7) "before" whom a breach of a vow was to be confessed (Lev 5:4-5).