Charles Ellicott Commentary Leviticus 12:4

"And she shall continue in the blood of [her] purifying three and thirty days; she shall touch no hallowed thing, nor come into the sanctuary, until the days of her purifying be fulfilled." — Leviticus 12:4 (ASV)

Continue in the blood of her purifying. —Better, continue in the blood of purification, that is, pure blood. Though the discharge following the birth ceases after two or three weeks, the period in this case, as in the former instance, is nearly doubled, to include exceptional cases. During these thirty-three days, which constituted the second stage, the mother was only prohibited from touching holy things, such as first tithes, the flesh of thank offerings and peace offerings, etc., and from entering the sanctuary. Having bathed at the end of the seven days which constituted the first and defiling period, she could now partake of the second tithes and resume conjugal intercourse, since any blood that might now appear was regarded as pure blood, in contrast to the (dam nidah) blood of monthly courses.

Her proximity, therefore, no longer defiled. The Sadducees and the Samaritans during the Second Temple, and their followers, the Karaite Jews, interpreted this law more rigidly. Though admitting that there is a difference of degree in the two periods, they maintained that the woman was too unclean for conjugal intercourse even during the second period. They therefore pointed the text differently to produce the rendering “blood of her purifying.” The Authorized Version, which, in this instance, follows the opinion of the Sadducees, departs from the received text.