They search out iniquities, &c.— They disguise their iniquities, and hide them with deep dissimulation: the inside and heart of every one of them is deep. See Mudge and Schultens.
Related Commentaries of Psalms 64:6
Psalms 64:6
6 They search out iniquities; they accomplish a diligent search: both the inward thought of every one of them, and the heart, is deep.