Reading through the Bible together
God created humans to multiply (Gen 1:28), so why should childbirth cause impurity? After the “Fall” (Gen 3), all humans are mortal and subject to death because of sin (Rom 6:23). When the immortal Creator of all life dwelt among mortals, He showed that His holy nature is different. Certain things, called “impure,” were associated with the birth to death cycle of mortality. These included blood, semen, and other fluids that flow from reproductive organs; also deteriorating skin; and corpses. Such impurity was not literal, but a category that emphasized the physical state of sinfulness that ends in death. Therefore, impurity was to be separated from holy things. Now that the earthly temple has ended, ritual purification is unnecessary. However, the record of the system still teaches us about our nature in relation to that of God.
After childbirth, a mother bled for several weeks, so she was impure. Perhaps because a baby girl can be born with blood in her genital area, so the mother would bear the baby’s impurity and twice as long if she had a boy. Emphasis on female impurity here does not devalue females below males, who could also have plenty of impurity (Lev 15). To complete her purification, the mother had to offer sacrifices, including a “sin offering.” This is better translated “purification offering” because she had not committed an act of sin and needed no forgiveness.