Bridges on Proverbs 20:17
Charles Bridges on Proverbs 20:17

17.  Bread of deceit is sweet to a man; but afterwards his mouth shall be filled with gravel. {deceit: Heb. lying, or, falsehood}
‘Holiness is sweet in the way and end too. Wickedness is sometimes sweet in the way, but always bitter in the end.’† It is with deceit, as with every other sin, Satan always holds out a bait; always promises gain or pleasure as the wages of his service, and as surely disappoints the victims of his delusion.† If corn be thrashed upon a gravelly floor, the grating soil would spoil the sweetness of the bread. Oh! how many has this arch-deceiver allured by the sweetness of his bread, whose mouths have been afterwards filled with gravel!The bread, which a man hath got by fraud and cozenage, seems sweet and pleasant at the first taste of it; but by that time he hath chewed it a little, he shall find it to be but harsh gravel, that crasheth between his teeth, galls his jaws, wounds his tongue, and offends his palate.’† ‘Everything gotten wrongfully is here implied.’† Bitter was Achan’s sweet, deceitfully hid in the tent, which brought ruin upon himself and his family. (Joshua 7:21-24.) Look at Gehazi. What profit had he from his talents of silver and changes of garments? Bitter indeed was the bread of deceit to him. (2 Kings 5:20-27.) Look even at Jacob, a true servant of God; and yet chastened heavily almost to the end of his days with the bitter fruits of deceit. (Genesis 27.; 42:36-38.) To the mass of such blinded sinners it is eternal ruin. Whatever be the tempter’s proffered advantage, his price is the soul, to be pain in the dying hour. Oh! the undoing bargain! an eternal treasure bartered for the trifle of a moment! Charmed we may be with the present sweetness; but bitter indeed will be the after-fruits, when the poor deluded sinner shall cry — “I tasted but a little honey, and I must die.” (1 Samuel 14:43.) So surely is the bitterness that springs out of sin the bitterness of death.
Not a single step can be trodden in the way of godliness, without an entire renunciation of every accursed practice. Not even the smallest violation of the law admits of palliation. To venture on what we fancy the lesser shades of sin is a most dangerous experiment. The smallest sin breaks down the fence; and this once overstepped, the impulse is beyond our restraint. Universal uprightness is the mark of the true servant of God. Let the man of doctrine exhibit the holiness of doctrine. Never let our religion be one thing, and our business another. But let the image and glory of the Lord give the pervading expression to our whole history. Every turning aside from the straight path “grieves the Holy Spirit of God,” darkens the sunshine of our soul, blasts the consistency of our profession, and wounds the church of God.