When the children of Israel left Egypt, they left with a mixed multitude.  That means that the there were Hebrews, Egyptians, and other slaves that came with them.  God gave specific instructions regarding these "foreigners".  In order to partake of the Passover, they had become circumcised, that is, the cutting away of the flesh.
Churches today also have mixed multitudes in their congregations.  The foreigners in the body, those not part of the covenant, must have a circumcision of the heart before being able to partake of communion.  Unfortunately, churches today are not making any requirements on the people in the church to become partakers of that covenant community.  We need to rediscover God's requirements.