Psalms 18:25 KJV

With the merciful thou wilt shew thyself merciful; with an upright man thou wilt shew thyself upright;
Psalms 18:25, King James Version

In context

24 Therefore hath the Lord recompensed me according to my righteousness, according to the cleanness of my hands in his eyesight.

25 With the merciful thou wilt shew thyself merciful; with an upright man thou wilt shew thyself upright;

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