John Calvin Commentary Psalms 109:7

"When he is judged, let him come forth guilty; And let his prayer be turned into sin." — Psalms 109:7 (ASV)

When he is judged, let him depart guilty. Another imprecation is that, being summoned to judgment, he may be punished without mercy, and that, though he humbly pleads for forgiveness, the judge should remain inexorable. This might properly be understood to relate not only to his being judged in human courts, but also at the tribunal of God.

But as it agrees very well with the decisions made by an earthly judge, and as this is the commonly accepted interpretation, I do not wish to depart from it. There are two things that must be noted here: that the wickedness of the wicked may be so palpable as to leave no room to escape from the execution of justice, and that all their entreaties for pardon may be disregarded.

Accordingly, the Psalmist represents him as a condemned criminal leaving the presence of the judge, bearing the ignominy of the condemnation that he righteously merited, having his nefarious deeds disclosed and detected. Regarding the other interpretation that places the ungodly before God’s judgment seat, it is by no means absurd to say that their prayers should be turned against them into sin, especially since we know that all their sacrifices are an abomination to Him.

And the more they themselves are filthy, the more all their plausible virtues become offensive and displeasing to God. But as the scope of the passage favors the interpretation that applies it to earthly judges, I do not consider it necessary to insist further on this point.