For a son or a daughter — For the birth of a son, or of a daughter: but the purification was for herself, as appears from the following verses. A sin — offering — Because of her ceremonial uncleanness, which required a ceremonial expiation.
Related Commentaries of Leviticus 12:6
Leviticus 12:6
6 And when the days of her purifying are fulfilled, for a son, or for a daughter, she shall bring a lamb of the firsta 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: