The Fulfillment
The purification of Mary was stipulated by Leviticus 12:1–8. A woman was considered to be unclean after the birth of a boy for forty days, and when her purification was finished she was to offer sacrifices for cleansing. Mary and Joseph offered either a pair of doves or two young pigeons (v. 24; cf. Lev. 12:8) because they could not afford to offer a lamb
(2) The Old Testament also required that the firstborn child should be redeemed by a payment of five shekels (Exod. 13:13; Num. 18:15–16). Such a “redemption” reflects the Old Testament tradition that the firstborn belongs to Yahweh. Luke does not say that the payment was made, perhaps because he has combined this theme with the next one.
(3) Interestingly, Luke combines the “redemption of the firstborn” with the presentation of Jesus to the Lord (vv. 22–23). Nowhere does the Old Testament require such a presentation, and the presentation of Jesus reminds one of Hannah’s presentation of Samuel (1 Sam. 1:22–24, 28). Perhaps Luke’s amalgamation of these three themes explains why he speaks of “their purification” in verse 22 because according to the Old Testament law only Mary needed to be purified.