John Trapp on Luke 2:22

Verse 22. And when the dayes of her purification] She was rather sanctified then polluted by bearing Christ, yet wrangleth not with the Law, nor claimeth an immunity. Now if she were so officious in ceremonies, what in the maine duties of morality? According to the Law] This Law of Purification proclaimes our uncleannesse, whose very birth infects the mother that bare us. She might not till the seventh day converse with men, nor till the fortieth day appear before God in the Sanctuary, nor then without a burnt-offering for thanksgiving, and a sin-offering for expiation of a double sin, viz. of the Mother that conceived, and of the Son that was conceived.