Why did the Mosaic Law say that sexual intercourse and childbirth made a person unclean?
The question arises: Why were such normal, proper things as menstruation, sexual intercourse between married persons, and childbirth viewed in the Law as making one unclean?
For one thing, it raised the most intimate relations of marriage to the level of sanctity, teaching both mates self-control, a high regard for the reproductive organs, and respect for the sacredness of life and blood. The hygienic benefits that accrued from scrupulous observance of these regulations have also been commented on. But there is yet another aspect of the matter.
In the beginning God created the sex impulses and generative powers in the first man and woman and commanded them to cohabit and bring forth children. It was therefore no sin for the perfect pair to have sexual intercourse. However, when Adam and Eve disobeyed God, not in the matter of sex relations, but in eating the forbidden fruit, drastic changes took place. Suddenly their guilty sin-stricken consciences made them aware of their nakedness, and they immediately covered their genital organs from Gods sight. (Ge 3:7, 10, 11) From then on, men could not carry out the procreative mandate in perfection, but, instead, the hereditary blemish of sin and the penalty of death would be transmitted from the parents to children. Even the most upright and God-fearing parents produce sin-infected children.Ps 51:5.
The Laws requirements pertaining to the functions of the reproductive organs taught men and women self-discipline, restraint of passions, and respect for Gods means of propagation.
The Laws regulations forcefully reminded creatures of their sinful state; these were not merely health measures to ensure cleanliness or prophylactic safeguards against the spread of diseases. As a reminder of mans inherited sinfulness, it was fitting that both the male and the female with genital discharges due to normal functions of their bodies observe a period of uncleanness. If suffering abnormal prolonged discharges because of defective conditions, a more extensive period of uncleanness was demanded; and in the end, as also when a mother gave birth, in addition to bathing, a sin offering was necessary, so that Gods priest might make atonement in behalf of the person. Jesus mother Mary thus confessed to her hereditary sinfulness, acknowledging that she was not sinless, immaculate, by offering a sin-atoning sacrifice after giving birth to her firstborn.Lu 2:22-24.