The Jewish law of purification declared that every woman who conceived and bore a male child was to be considered unclean for seven days. After the circumcision of the child, the mother was to remain in her house for thirty-three days. She was not to touch any holy thing and was not to enter the sanctuary. After the days of her purification had been fulfilled, she was to present to the priest at the entrance of the Tabernacle a young yearling lamb as a burnt offering and a young pigeon or turtle dove as a sacrifice for sin. If she was too poor to procure a lamb, she was to offer two turtledoves or two young pigeons. The priest was to make expiation(atonement) for her and she was then considered clean (Leviticus 12:2-8).
The immaculate Virgin, who had conceived of the Holy Spirit and became a mother while keeping her virginity, did not come under the Law that touched the other daughters of Israel. If she submitted to it, it was only to imitate her Son (who was to be baptized by John) and to avoid scandal for her acquaintances, who knew nothing of her virginal motherhood.
A first-born male child belonged to the Lord by the double title of first-fruit and head of the family. In patriarchal societies heads of families exercise a sort of priesthood. Theirs is the right of offering sacrifice and on them falls the duty of caring for divine worship.
In Israel the priestly tribe of Levi had been given this office, but firstborn sons continued nonetheless to be consecrated to god and he had to be brought back at a set price (Numbers 3:12-13). The payment of this ransom was due the thirtieth day after birth and was to be made by the child's father. The place of payment was not prescribed, nor confined to the Temple. Nor was the mother obliged to go to Jerusalem for the ceremony of purification; she was allowed to offer her sacrifice by proxy. Pious Jews who did not live too far from the Holy City made it a point to appear personally in the Lord's presence; and that is what the Evangelist supposes in Mary's case: "When the time of their purification had been completed according to the Law of Moses, they carried the child to Jerusalem to present him to God, as it is wirtten in the Law of the Lord: Every first-born male shall be consecrated to the Lord" (Luke 2:23).
While the Holy family was carrying out these legal presciptions, a resident of Jerusalem unexpectedly came up to them. He was Simeon, a just man who feared God and firmly hope the Consoler of Israel was soon to come. The Holy Spirit had assured him that he would not die before seeing the Anointed of the Lord. Why he was there we do not know, for he was not a priest and was not called there for some sacred duties to perform. In any event, the stranger took the divine child in his arms and gave expression to his joy in his canticle of thanksgiving: