Though he wist it not— Though he knew it not. It is the same word as has been used throughout the chapter, and refers to sins of ignorance.
Related Commentaries of Leviticus 5:17
Leviticus 5:17
17 And if a soul sin, and commit any of these things which are forbidden to be done by the commandments of the LORD; though he wist it not, yet is he guilty, and shall bear his iniquity.