Foreskin

You are to circumcise the flesh of your foreskin, and this will be a sign of the covenant between Me and you.

But Zipporah took a flint knife, cut off her son’s foreskin, and touched it to Moses’ feet. “Surely you are a bridegroom of blood to me,” she said.

And on the eighth day the flesh of the boy’s foreskin is to be circumcised.