Feast of the Purification and the Presentation of Jesus in the Temple

Forty days after birth the first-born son was presented to God in the temple in Jerusalem and the mother went also for the rite of "purification" - Mary and Joseph were devout Jews and so went to the Temple to fulfill the law. While they were there, two others, both people of prayer, were privileged to have the Son of God revealed to them. Simeon had been waiting for this moment. He exclaimed, on seeing the Infant Jesus, and we have his beautiful canticle that is said every day still in the official prayers of the Church's daily Office:

Nunc Dimittis (Canticle of Simeon; Luke 2:29-32): "Now thou dost dismiss thy servant, O Lord, according to thy word in peace; because my eyes have seen thy salvation, which thou hast prepared before the face of all peoples: a light to the revelation of the Gentiles, and the glory of thy people Israel."
History:
Known originally as the Feast of the Purification of the Blessed Virgin, the Feast of the Presentation of the Lord is a relatively ancient celebration. We know that the Church at Jerusalem was observing the feast as early as the first half of the fourth century, and likely earlier.

According to Jewish law, the firstborn male child belonged to God, and the parents had to "buy him back" on the 40th day after his birth, by offering a sacrifice of "a pair of turtledoves, or two young pigeons" (Luke 2:24) in the temple (thus the "presentation" of the child). On that same day, the mother would be ritually purified (thus the "purification").

St. Mary and St. Joseph kept this law, even though, since St. Mary remained a virgin after the birth of Christ, she would not have had to go through ritual purification. In his gospel, Luke (2:22-39) recounts the story.

Originally, the feast was celebrated on February 14, the 40th day after Epiphany (January 6), because Christmas wasn't yet celebrated as its own feast, and so the Nativity, Epiphany, the Baptism of the Lord (Theophany), and the feast celebrating Christ's first miracle at the wedding in Cana were all celebrated on the same day. By the last quarter of the fourth century, however, the Church at Rome had begun to celebrate the Nativity on December 25, so the Feast of the Presentation was moved to February 2, 40 days later.