However, as the congregation relates to the local Church.
A congregation is a group of the people who profess to be of the body of Christ, they profess to have the vision and goal to save. Only God knows those who are members of His true Church.
Romans 9:6-7. Not as though the word of God hath taken none effect. For they are not all Israel, which are of Israel: Neither, because they are the seed of Abraham, are they all children: but, In Isaac shall thy seed be called.
Matthew 7:21. Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
God will do the final sorting and reveal/redeem His true Church:
Matthew 13:30. Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.