Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
Lev 12-15. Ceremonial Purifications
The Purifications of the Law fall under three heads;
(1). Those for defilement arising from secretions;
(2). Those for the leprosy;
(3). Those for pollution from corpses.
The first and second classes are described in these chapters; the last, as relates to human corpses, in Num 19:11, etc., and as relates to the bodies of dead animals, in Lev 11:24-28, Lev 11:31-40.
This chapter would more naturally follow the 15th chapter of Leviticus. See the note to Lev 15:1.
On circumcision, see Gen 17:5 note.
The Levitical law ascribed impurity exclusively to the mother, in no degree to the Child.
Some have thought that this doubling of each of the two periods was intended to remind the people of the fact that woman represents the lower side of human nature, and was the first to fall into temptation. Ti1 2:13-15; Pe1 3:7. The ancients had a notion that the mother suffers for a longer time after the birth of a girl than after the birth of a boy. The period required for the restoration of her health in the one case was thirty days, and in the other, it was 40 or 42 days. This notion may have been connected with a general custom of observing the distinction as early as the time of Moses.
The sacrificial act expressed an acknowledgment of sin and a dedication of herself to Yahweh. See Lev 8:14.
Of the first year - literally, as in the margin, "a son of his year." This expression is supposed to mean one less than a year old, while the "son of a year" is one that has just completed its first year.
A lamb - Rather, one of the flock; either a sheep or a goat; it is not the same word as in Lev 12:6.
Two turtles, or two young pigeons - See the note at Lev 1:14. The Virgin Mary availed herself of the liberty which the Law allowed to the poor, and offered the inferior burnt-offering Luk 2:24.