“Say to the Israelites, ‘A woman who becomes pregnant and gives birth to a son will be unclean for seven days, as she is during the days of her menstruation.
2. If a woman have conceived seed. This ceremony had reference to two points; for, first, the Jews were reminded by it of the common corruption of our nature; and secondly, the remedy of the evil was set before them.
The law here pronounces women lying-in ceremonially unclean. The Jews say, "The law extended even to an abortion, if the child was so formed as that the sex was distinguishable." 1. There was some time of strict separation immediately after the birth, which continued seven days for a son and fourteen for a daughter, Lev 12:2, Lev 12:5.
Commenting on Leviticus 12:1-5
Speak unto the children of Israel,.... For this law only concerned them, and not other nations of the world: if a woman have conceived seed; by lying with a man, and so becomes pregnant, and goes on with her pregnancy until she brings forth a child.