C. F. Keil and Franz Delitzsch on Proverbs 18:5

Pro 18:5 5 To favour the person of the godless is not good,    And to oppress the righteous in judgment.

As Pro 18:4 has one subject, so Pro 18:5 has one predicate. The form is the same as Pro 17:26. שׂאת פּני (cf. Pro 24:23), προσωποληψία, acceptio personae, is this, that one accepts the פני, i.e. the personal appearance of any one (πρόσωπον λαμβάνει), i.e., regards it as acceptable, respectable, agreeable, which is a thing in itself not wrong; but in a judge who ought to determine according to the facts of the case and the law, it becomes sinful partiality. הטּות, in a forensic sense, with the accus. of the person, may be regarded in a twofold way: either as a turning aside, מדּין, Isa 10:2, from following and attaining unto the right, or as an oppression, for the phrase הטּה משׁפּט [to pervert justice] (cf. Pro 17:23) is transferred to the person who experiences the oppression = perversion of the law; and this idea perhaps always underlies the expression, wherever, as e.g., Mal 3:5, no addition brings with it the other. Under Pro 17:15 is a fuller explanation of לא־טוב.