The writings of Luke the physician starting with his version of the gospel - Luke 2:21-24 comments; Mary and Joseph obey the Law given to Moses

Luke 2:21 ¶  And when eight days were accomplished for the circumcising of the child, his name was called JESUS, which was so named of the angel before he was conceived in the womb. 22  And when the days of her purification according to the law of Moses were accomplished, they brought him to Jerusalem, to present him to the Lord; 23  (As it is written in the law of the Lord, Every male that openeth the womb shall be called holy

to the Lord;) 24  And to offer a sacrifice according to that which is said in the law of the Lord, A pair of turtledoves, or two young pigeons.

Here is the original requirement for the circumcision of Hebrew baby boys given to Abraham.

Genesis 17:12  And he that is eight days old shall be circumcised among you, every man child in your generations, he that is born in the house, or bought with money of any stranger, which is not of thy seed.

Then under the Law given to Moses. Note the poverty of Mary and Joseph underscored by this passage. You can’t get too much more humble than this; born in a stable which may have been a cave, a feeding trough for a crib, and a mother and step-father who were poor as the proverbial church mouse.

Leviticus 12:2  Speak unto the children of Israel, saying, If a woman have conceived seed, and born a man child: then she shall be unclean seven days; according to the days of the separation for her infirmity shall she be unclean. 3  And in the eighth day the flesh of his foreskin shall be circumcised…6 ¶  And when the days of her purifying are fulfilled, for a son, or for a daughter, she shall bring a lamb of the first year for a burnt offering, and a young pigeon, or a turtledove, for a sin offering, unto the door of the tabernacle of the congregation, unto the priest: 7  Who shall offer it before the LORD, and make an atonement for her; and she shall be cleansed from the issue of her blood. This is the law for her that hath born a male or a female. 8  And if she be not able to bring a lamb, then she shall bring two turtles, or two young pigeons; the one for the burnt offering, and the other for a sin offering: and the priest shall make an atonement for her, and she shall be clean.

As the Law required.

Exodus 13:12  That thou shalt set apart unto the LORD all that openeth the matrix, and every firstling that cometh of a beast which thou hast; the males shall be the LORD’S.