'Foreskin' in the Bible

And you shall be circumcised in the flesh of your foreskins, and it shall be the sign (symbol, memorial) of the covenant between Me and you.

Then Zipporah took a flint knife and cut off the foreskin of her son and threw it at Moses’ feet, and said, “Indeed you are a husband of blood to me!”

So circumcise [that is, remove sin from] your heart, and be stiff-necked (stubborn, obstinate) no longer.