Could you explain the importance of waiting eight days for circumcision?

Answer:

"Speak to the children of Israel, saying: 'If a woman has conceived, and borne a male child, then she shall be unclean seven days; as in the days of her customary impurity she shall be unclean. And on the eighth day the flesh of his foreskin shall be circumcised. She shall then continue in the blood of her purification thirty-three days. She shall not touch any hallowed thing, nor come into the sanctuary until the days of her purification are fulfilled" (Leviticus 12:2-4).

Whenever a woman had her monthly blood flow, she was unclean for seven days. "If a woman has a discharge, and the discharge from her body is blood, she shall be set apart seven days; and whoever touches her shall be unclean until evening. Everything that she lies on during her impurity shall be unclean; also everything that she sits on shall be unclean. Whoever touches her bed shall wash his clothes and bathe in water, and be unclean until evening. And whoever touches anything that she sat on shall wash his clothes and bathe in water, and be unclean until evening. If anything is on her bed or on anything on which she sits, when he touches it, he shall be unclean until evening" (Leviticus 15:19-23). Since a birth also includes a blood flow, the mother is unclean for seven days and technically so is the child. So waiting until the eighth day takes both the mother and child past the week of uncleanness.

Interestingly, we have learned in recent years that prothrombin, which is essential in blood clotting, peaks in a child eight days after birth, making the eighth day the safest for a child to receive a wound. Vitamin K is necessary to produce prothrombin but that vitamin is produced by bacteria in the intestine. It takes several days (seven as a matter of fact) for the bacteria to get established and start producing sufficient quantities of vitamin K. Prothrombin is actually present in greater than normal quantities on the eighth day before it settles down to a steady level. Because vitamin K levels are low from the second to fifth days after birth, wounds can be dangerous for a child. [Bert Thompson, "Biblical Accuracy and Circumcision on the 8th Day," Apologetics Press]

In countries where circumcision is practiced, it is standard procedure to give a child a vitamin K shot because the doctors don't wait for the eighth day to do the surgery. Of course, the New Testament declares that circumcision is an unnecessary procedure. "For in Christ Jesus neither circumcision nor uncircumcision avails anything, but faith working through love" (Galatians 5:6).