Albert Barnes' Notes on the Whole Bible - Psalms 18:26
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... read more
The Pulpit Commentary - Psalms 18:26
With the pure thou wilt show thyself pure; and with the froward thou wilt show thyself froward; rather, thou wilt show thyself adverse. The same root is not here used for the verb as for the adjective, as is done in the three preceding clauses. The reason is well explained in the 'Speaker's Commentary:' "In dealing with the good, God shows his approval by manifesting attributes similar or identical in essence; in dealing with the wicked, he exhibits attributes which are correlative—in... read more