Matthew Poole and continuators on Leviticus 5:6

6 And he shall bring his trespass-offering unto the LORD for his sin which he hath sinned, a female from the flock, a lamb or a kid of the goats, for a sin-offering: and the Priest shall make an atonement for him concerning his sin.

Quest. How comes confession and a sacrifice to be necessary for him that touched an unclean thing, when such persons were cleansed with simple washing, as appears from Levit. 11. and Numb. 19? Ans. This place speaks of him that being so unclean did come into the Tabernacle, as may be gathered by comparing this place with Numb. 19. 13. which if any man did knowing himself to be unclean, which was the case there, he was to be cut off for it; and if he did it ignorantly, which is the case here ver. 2. he was upon discovery of it to offer this sacrifice. Interpreters dispute much what the difference is between sins and trespasses, and between si[illegible: 1+ letters]-offerings and trespass-offerings. Some make the one for omissions the other for commissions the one for greater, the other for lesser sins, the one for known sins, the other for sins of ignorance. In all which there seems to be more curiosity than solidity. Either they seem to be the same▪ as may be gathered from [illegible: 1 word]. 6. where those two words, asham, and chata, which they so carefully and critically distinguish, are both used concerning the trespass-offerings, and from [illegible: 1 word]. 9. or the difference may be this, that sin-offerings were more indefinite or general, being for any particular sin, and trespass-offerings more restrained and particular for such sins as were more scandalous and injurious either to God by blasphemy, as ver. 1. or to his Sanctuary, by approaching to it in ones uncieanness, ver. 2, 3. as hath been now said; or to ones neighbour by swearing to do to them either the good which we afterwards cannot or do not, or the evil which we should not; or to the Priests and holy things of God, ver. 15.

Because those sins were less than others, as being committed ignorantly or unwittingly▪ and therefore God would accept a meaner sacrifice for them.