Albert Barnes Commentary Psalms 18:26

"With the pure thou wilt show thyself pure; And with the perverse thou wilt show thyself froward." — Psalms 18:26 (ASV)

With the pure – Those who are pure in their thoughts, their motives, their conduct.

Thou wilt show thyself pure – They will find that they have to deal with a God who is Himself pure; who loves purity, and who will accompany it with appropriate rewards wherever it is found.

And with the froward – The word used here – עקשׁ ‛iqqêsh – means properly perverse: a man of a perverse and wicked mind. It is derived from a verb – עקשׁ ‛âqash – which means to turn the wrong way, to wrest, to pervert. It would be applicable to a man who perverts or wrests the words of others from their true meaning; who prevaricates or is deceitful in his own conduct; who is not straightforward in his dealings; who takes advantage of circumstances to impose on others and to promote his own ends; who is sour, harsh, crabbed, unaccommodating, unyielding, unkind. It is rendered perverse in (Deuteronomy 32:5), (Proverbs 8:8), (Proverbs 19:1), and (Proverbs 28:6); froward here, and in (2 Samuel 22:27), (Psalms 101:4), (Proverbs 11:20), (Proverbs 17:20), and (Proverbs 22:5); and crooked in (Proverbs 2:15).

The word does not occur elsewhere in the Old Testament.

Thou wilt show thyself froward – The marginal reading is wrestle. In the corresponding place in (2 Samuel 22:27) it is rendered, “Thou wilt show thyself unsavory;” though the same word is used in the original. In the margin in that place, as here, the word is wrestle. The original word in each place – פתל pâthal – means to twist, to twine, to spin; and then, to be twisted; to be crooked, crafty, deceitful. In the form of the word that occurs here (Hithpael), it means to show oneself crooked, crafty, perverse (Gesenius, Lexicon). It cannot mean here that God would assume such a character, or that He would be crooked, crafty, perverse in His dealings with people. For no one can suppose that the psalmist meant to ascribe such a character to God. The meaning plainly is that God would deal with the person referred to according to their real character: instead of finding that God would deal with them as if they were pure, righteous, and merciful, such people would find that He deals with them as they are – as perverse, crooked, wicked.