C. F. Keil and Franz Delitzsch on Proverbs 17:15

Pro 17:15 15 He that acquitteth the guilty and condemneth the righteous -      An abomination to Jahve are they both.

The proverb is against the partisan judge who is open to bribery, like Pro 24:24, cf. Isa 5:23, where, with reference to such, the announcement of punishment is emphatically made. רשׁע and צדּיק, in a forensic sense, are equivalent to sons (reus) and insons. גּם (cf. the Arab. jmy'na, altogether, but particularly the Pers. ham and the Turkish dkhy standing wholly thus in the numeral) is here, as at Gen 27:45, equivalent to יחדּיו, Jer 46:12 (in its unions = united). Whoever pronounces sentence of justification on the guilty, appears as if he must be judged more mildly than he who condemns the guiltless, but both the one and the other alike are an abhorrence to God.

We take Pro 17:16-21 together. This group beings with a proverb of the heartless, and ends with one of the perverse-hearted; and between these there are not wanting noticeable points of contact between the proverbs that follow one another.