"In his account of the infancy of Jesus St Luke emphasizes how faithful Mary and Joseph were to the Law of the Lord. They fulfilled with profound devotion all the prescriptions prescribed following the birth of a firstborn male. Two of them were very ancient prescriptions: one concerns the mother and the other the newborn child. The woman was required to abstain from ritual practices for forty days, after which she was to offer a double sacrifice: a lamb as a burnt offering and a turtle-dove as a sin offering; but if she were poor, she could offer a pair of turtle doves or two young pigeons (cf. Lev 12:1-8).
St Luke explained that Mary and Joseph offer the sacrifice of the poor (cf. 2:24) in order to emphasize that Jesus was born into a family of simple people, lowly but of steadfast faith: a family that belonged to the poor of Israel who form the true People of God. For the first-born male who, according to Mosaic Law, was set apart for God, redemption was prescribed instead, established as an offering of five shekels to be paid to a priest in any place. This was in everlasting memory of the fact that in the time of Herod God saved the firstborn of the Jews (cf. Ex 13:11-16).
It is important to note that these two acts — the purification of the mother and the redemption of the son — did not require a visit to the Temple. However, Mary and Joseph wished to fulfill all the prescriptions in Jerusalem, and St Luke shows us how the entire scene converges on the Temple and thus focuses on Jesus who enters it. And it is here, precisely through the prescriptions of the Law, that the principal event is transformed, namely, it becomes the “presentation” of Jesus in the Temple of God, which means the act of offering the Son of the Most High to the Father who sent him (cf. Lk 1:32, 35).
The Evangelist’s account is confirmed by the words of the Prophet Malachi which we heard at the beginning of the First Reading: “Behold”, says the Lord, “I send my messenger to prepare the way before me, and the Lord whom you seek will suddenly come to his temple; the messenger of the covenant in whom you delight, behold, he is coming... he will purify the sons of Levi.... Then the offering... will be pleasing to the Lord” (3:1, 3, 4)."
Pope Benedict XVI, Feb. 2nd, 2013