Posted by: Rob Lester | March 30, 2010

Why circumcision on the eighth day?

God commanded Abraham to circumcise newborn males on the eighth day.  Why that day?  Blood clotting depends heavily upon two nutrients:  vitamin K and prothrombin.  A baby boy’s body does not produce adequate levels of vitamin K until days 5-7.  On the eighth day, prothrombin is elevated high above 100% of normal.  This is the only day in a male’s life that this will occur.  A medical doctor once observed, “Abraham did not pick the eighth day after many centuries of trial and error…it was a day picked by the Creator of vitamin K” (McMillen 21).  Who better understands the function of a machine than its inventor?  It wasn’t a lucky guess.  It was a divine command made through the perfect knowledge of God.

McMillen, S.I. None of These Diseases. 1963.)



  1. wasn’t abraham’s son the first infant to be circumcised?

  2. Abraham received the command in Genesis 17:12 along with the promise of Isaac being born. It would have been at least nine months (and likely longer) before Isaac was born to be circumcised. It is also likely that a baby boy was born in Abraham’s household in that period who would have been circumcised. But, we don’t have specific record of it, so it is at least possible that Isaac was the first baby circumcised.

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