Solomon
Proverbs 20:17ESV·traditional attribution

Bread gained by deceit is sweet to a man, but afterward his mouth will be full of gravel.

Matthew Henry Presbyterian @wholebiblehenry

Note, 1. Sin may possibly be pleasant in the commission: Bread of deceit, wealth gotten by fraud, by lying and oppression, may be sweet to a man, and the more sweet for its being ill-gotten, such pleasure does the carnal mind take in the success of its wicked projects. All the pleasures and profits of sin are bread of deceit.

John Gill Reformed Baptist @doctorgill

Bread of deceit is sweet to a man,.... Which may be understood of sin in general, which is bread to the sinner, he eats it: it is called "the bread of wickedness", Pro 4:17; but it is but poor bread, no other than ashes Isa 44:20; it is "bread of deceit"; there is a deceitfulness in all sin; it is in appearance fair and pleasant...

Jamieson-Fausset-Brown Reformed @jfbcommentary

Bread . . . sweet--either as unlawfully (Pro 9:17) or easily obtained. mouth . . . gravel--well expresses the pain and grief given at last.