In the Bible, the period of 40 days after childbirth is known as the "purification period" or "consecration period" for the mother. This period is mentioned in Leviticus 12:1-8, where it is stated that a woman who gives birth to a male child is considered unclean for seven days. After that, she must remain at home for 33 days to complete her purification period, making a total of 40 days.

During this time, the mother is not allowed to touch anything holy or enter the sanctuary. She is also not allowed to have sexual relations with her husband until the end of her purification period. After the 40 days, she is required to bring a burnt offering and a sin offering to the priest at the entrance of the tent of meeting to complete her purification.

The same rules apply for a woman who gives birth to a female child, but the purification period is extended to 14 days, making a total of 80 days.

The purpose of this purification period was to emphasize the importance of childbirth and to recognize the woman's role in bringing new life into the world. It also served as a reminder of the holiness of God and the need for purity before approaching Him.

In the New Testament, Mary, the mother of Jesus, also observed the purification period after giving birth to Jesus. In Luke 2:22-24, it is stated that Mary and Joseph took Jesus to the temple to present Him to the Lord and to offer the sacrifices required by the Law of Moses. This was done after the completion of Mary's purification period.

In conclusion, the Bible states that a woman who gives birth is considered unclean for a period of time and must observe a purification period of 40 days (or 80 days for a female child). This was a way to emphasize the importance of childbirth and the need for purity before approaching God. Mary, the mother of Jesus, also observed this period after giving birth to Jesus.