Psalms 18:26

With the pure thou wilt shew thyself pure; and with the froward thou wilt shew thyself froward.

The verse belongs to David's testimony that the Lord recompensed him according to his righteousness and the cleanness of his hands because he had kept the ways of the Lord and His judgments and statutes and had remained upright before Him. It declares that God responds to people according to the character and spirit they bring to Him. To the merciful He shows Himself merciful, to the upright He shows Himself upright, and to the pure He shows Himself pure. To the froward He shows Himself froward, meeting their crookedness with a corresponding response in kind.

In the parable of the laborers this means that those who trust God instead of bargaining for a fixed reward serve Him with thankfulness and joy, while those who insist on a stated wage receive no more than the amount they specified. As God meets people where they are, so people are to meet others where they are. Refusing to do so can place them outside the compass of God's love and mercy, while uprightness is rewarded by Him.