"which in other ages was not made known to the sons of men, as it has  now been revealed by the Spirit to His holy apostles and prophets:"  Ephesians 3:5  NKJV

Those who went before Paul did not know because God did not reveal it to them. There are many things that are better left unsaid. The last word in an argument. A bitter word to a close friend or family member. Words muttered to self under our breath.

This verse does not refer to words better left unsaid, but to words that didn't make sense to the hearers. The meaning was scrambled or understood to mean something else. The same words now are understood to mean the Gentile and Jew are made one through the blood of the Lamb, {Jesus Christ}. 

This oneness is referred to the people of God or the body of Christ, with Jesus being the head. What good is a body without the head? You guessed it: Nothing. The head gives all the commands to move here or there or to stay in one place. The head or brain is the center for all speech and thought.

What difference would God's people make on the earth without Jesus? The people of God would be of no effect if he were not within them. It is impossible to belong to Christ, and not be  attached. No one can run on their own without the head.

Belonging to a local church body is important for several reasons. The act of belonging brings safety to every individual because we were made for this. God made us to rely on each other. Someone has to be able to give us perspective from the outside of our own world.

A Pastor is to watch his people to guard each soul from trouble. This is called accountability. Without it we can easily be deceived and fall into sin. A close church group in larger churches is built especially for this. A spiritual mentor can help a pastoral staff to keep the flock safe.

We were made for relationship with God and his people. Those around us need to be careful to speak words of truth and life so that we can prosper spiritually. Love has to be the motive of the heart. Without the love of God all of this is just a dream.