With the pure thou wilt shew thyself pure (barar); and with the froward (iqqesh) thou wilt shew thyself froward (pathal).
pure (barar) (Hithpael verb stem): to purify oneself; to show oneself pure, just, kind
froward (iqqesqh): twisted, distorted, crooked, perverse, perverted
froward (pathal) (Hithpael verb stem): to be twisted
Psalm 18:25-26 NASB:
With the kind You show Yourself kind; with the blameless You show Yourself blameless; with the pure You show Yourself pure, and with the crooked You show Yourself astute.