The blood of her purifying - A few words will make this subject sufficiently plain.

1. God designs that the human female should bring forth children.

2. That children should derive, under his providence, their being, all their solids and all their fluids, in a word, the whole mass of their bodies, from the substance of the mother.

3. For this purpose he has given to the body of the female an extra quantity of blood and nutritious juices.

4. Before pregnancy this superabundance is evacuated at periodical times.

5. In pregnancy, that which was formerly evacuated is retained for the formation and growth of the fetus, or the general strengthening of the system during the time of pregnancy.

6. After the birth of the child, for seven or fourteen days, more or less according to certain circumstances, that superabundance, no longer necessary for the growth of the child as before, continues to be evacuated: this was called the time of the female's purification among the Jews.

7. When the lacerated vessels are rejoined, this superfluity of blood is returned into the general circulation, and, by a wise law of the Creator, becomes principally useful to the breasts, and helps in the production of milk for the nourishment of the new-born infant.

8. And thus it continues till the weaning of the child, or renewed pregnancy takes place. Here is a series of mercies and wise providential regulations which cannot be known without being admired, and which should be known that the great Creator and Preserver may have that praise from his creatures which his wonderful working demands.

The term purifying here does not imply that there is any thing impure in the blood at this or the other times referred to above; on the contrary, the blood is pure, perfectly so, as to its quality, but is excessive in quantity for the reasons above assigned. The idle tales found in certain works relative to the infectious nature of this fluid, and of the female in such times are as impious as they are irrational and absurd.

Leviticus 15:25-28 And if a woman have an issue of her blood many days out of the time of her separation, or if it run beyond the time of her separation...

Haggai 2:13 Then said Haggai, If one that is unclean by a dead body touch any of these, shall it be unclean? And the priests answered and said...

Luke 2:22,23 And when the days of her purification according to the law of Moses were accomplished, they brought him to Jerusalem...

The Early Years of Jesus
Matt. i. 1 to ii. 23; Luke i. 5 to ii. 52; iii. 23-38 58. It is surprising that within a century of the life of the apostles, Christian imagination could have so completely mistaken the real greatness of Jesus as to let its thirst for wonder fill his early years with scenes in which his conduct is as unlovely as it is shocking. That he who in manhood was "holy, harmless, undefiled, separate from sinners" (Heb. vii. 26), could in youth, in a fit of ill-temper, strike a companion with death and then …
Rush Rhees—The Life of Jesus of Nazareth