The Bible constantly mentions both circumcision and yeast. Circumcision affects a very delicate and personal part of a human and changes a person and yeast is something that totally affects something and changes that thing. So both circumcision and yeast change things. They are both separate things from the original thing that was made by God. But the heart which is also mentioned in the Bible is originally made by and known by God and the heart is examined by God to see if it’s His.