Psalm 51/Notes/Lexical.v. 6.443634

זכה in Classical Hebrew means to be "upright and innocent in character and behavior," which in context means that God cannot be faulted (and therefore is vindicated against all possible charges of injustice) when he judges. There is an intentional blending of metaphors here, where God is judged by others in his capacity as judge. The qal vocalization suggests that the verb refers to God's faultless character that results in his vindication, whereas a passive construction might have been expected if תזכה were referring to the act of his vindication (so NIV "justified"). Several ancient versions translate תִּזְכֶּה with the sense "be victorious" (e.g., LXX νικήσῃς), which seems to be a metaphorical extension of the concept of vindication in court. The fully developed meaning "to win" appears to be a late development in the Hebrew language without clear parallel in Classical Hebrew texts. The ISV reading "clear" seems to imply clear-sightedness or clear thinking on the part of God rather than his being "in the clear" when others are critiquing his judgments; this sense is not attested for this verb and disrupts the parallel with תִּצְדַּק.