Many articles have been written to explain the difference between the period of impurity of mothers giving birth to boy child and of mothers giving birth to a girl child. I ask a different question: Why should Tazria, the Torah portion that we read this week that concentrates on skin lesions, start with the purification laws of women who give birth?
The Torah says that you shall not work on Shabbat, and the next Torah portion is the building of the Mishkan; the rabbis concluded that the work for building the Mishkan constitutes the 39 categories of work that are forbidden on Shabbat.
Nadav and Avihu offered a strange fire to God and died, and the next passage is God’s telling Aaron you shall not drink wine or beer before you minister to God; the rabbis concluded that Avihu and Nadav were drunk.
What’s the connection between the impurity period of a mother giving birth and skin lesions?
Tazria doesn’t contain a counterpart purification ritual for skin lesions like it does for giving birth.
The only thing I see, is the time period. A mother is unclean for seven days for birthing a boy child, and a mother is unclean for two weeks for birthing a girl child.
The priest inspects the skin lesions first, and the priest returns seven days later. If on the seventh day, the priest finds the sore is not healed, he waits another seven days. After the second, seven-day period, the priest pronounces him clean (if the sore has healed) or pronounces him unclean (if the sore has not healed).
If you have another explanation of why the birth of child begins Tazria, I would love to hear it.