Those weren't Mary's sin offering due to her being in sin. Were she unclean she would not have been able to fulfill God's law of the firstborn and thus enter the temple.
The Law of the Firstborn
...Fulfilling the Law
Many years passed in the land of Israel. Much history transpired, and a great many things changed. Even though the Levitical priesthood was becoming increasingly corrupt, God's rules regarding the firstborn were still upheld among the remnant of the Jews. Now
Jesus Christ, who had just come into
the world as a firstborn—both of His heavenly Father and of His physical mother, Mary—was about to begin a life of obedience to His own laws:
And she brought forth her firstborn Son, and wrapped Him in swaddling cloths, and laid Him in a manger, because there was no room for them in the inn. . . . And when eight days were completed for the circumcision of the Child, His name was called Jesus, the name given by the angel before He was conceived in the womb. (
Luke 2:7, 21)
On Jesus' eighth day of life, He was circumcised, and, as a firstborn, He was dedicated to God's service. It is interesting that Luke makes no mention of Mary and Joseph offering a lamb as a redeeming sacrifice, though he does record the sin and burnt offerings that they presented later on the fortieth day of His human life:
Now when the days of her purification according to the law of Moses were completed, they brought Him to Jerusalem to present Him to the Lord (as it is written in the law of the Lord, "Every male who opens the womb shall be called holy to the Lord") and to offer a sacrifice according to what is said in the law of the Lord, "A pair of turtledoves or two young pigeons." (
Luke 2:22-24)
This omission appears to be because:
1. Jesus Himself was to become the redeeming sacrifice to which all other redeeming sacrifices had pointed since Moses' time;
2. His physical life was now completely dedicated to God, as had been pictured by all the other firstborn since Moses' time; and
3. He was not to be redeemed from a life of total service to God, neither by the offering of a lamb nor by the service of the now corrupt Levitical priesthood. The imperfect Levitical priesthood, which had pictured His perfect life of service since Moses' day, was soon to be set aside, and His own priesthood (after the order of
Melchizedek; see
Hebrews 6:20) would be reinstated.
The offering of the two turtledoves or pigeons refers to the fortieth-day purification, not to the fact that Jesus was the firstborn. Again, this purification offering was required for all births, not just for the firstborn. Luke adds in Luke 2:27: "And when the parents brought in[to the Temple] the Child Jesus, to do for Him according to the custom of the law . . ." (Luke 2:27).
This "custom of the law" refers specifically to the fortieth-day purification offering at the Temple. This is proven by both Mary and Joseph being in attendance, a thing she could not do if she were still unclean. Mary was ceremonially unclean on Jesus' eighth day of life, when the firstborn and circumcision ceremonies were performed at home, not at the Temple (see Luke 1:57-59 regarding the circumcision of John the Baptist). Ceremonial purity was not necessary for these latter rituals.