John Calvin Commentary Psalms 101:4

"A perverse heart shall depart from me: I will know no evil thing." — Psalms 101:4 (ASV)

The perverse heart shall depart from me. Some understand perverse heart to mean perfidious men; but I reject this interpretation as too forced, and it is moreover inconsistent with the context. As David has added in the second clause by way of exposition, I will not know evil, he doubtless protests in the first clause that he will be free from all perfidiousness and wickedness. The meaning is that he will strive to keep himself from all wrongdoing, and that he will not even know what it is to do wrong to his neighbors.