“If anyone sins unintentionally in any of the LORD's commandments about things not to be done, and does any one of them ….” (4:2). Priests and leaders as well as the “whole community” of Israel were ordinary humans, and therefore prone to mistakes (v3,13,22), such as accidentally breaking ritual laws or forgetting their obligations. Moses instructed them that even these “small things” would create a barrier between them and the Holy God who wanted to live among them, and so they offered sacrifices.
“He shall be forgiven” (v35). God’s desire is for fellowship with us, without distance, and so He always provides a means of reconciliation.