In Ephesians 4:3, 13 Paul speaks about the necessity of unity in the Body. He says that as believers, we must all "preserve the unity of the spirit … until we attain to the unity of the faith". There may be many areas where as believers we do not see eye-to-eye. You may not agree with my view that the church will go through the tribulation before Christ comes to take her up to Himself. You may feel that Christ will come before the tribulation. There could be other differences of opinion like that. We have not attained to unity in ALL matters of the faith. But until we do, we must be united in spirit. We don't have to wait until we are united in all matters of the faith before we are united in spirit.
We are to grow up gradually "to a mature man, to the fullness of the stature of Christ" (Eph. 4:13). Our aim must be to grow ourselves and to help others to grow to this fullness. We must not remain babies "tossed here and there by waves and carried about by every wind of doctrine, by the trickery of men, by craftiness in deceitful scheming" (Eph. 4:14).
God allows us to be exposed to deception and false teaching so that we can grow in discernment. Our sense of discernment will not be developed otherwise. That's why He allows so many deceivers and false prophets to move around in Christendom. Thus we will be able to discern the one whose spirit is not right from the one whose spirit is right. We don't have to judge others. But we must discern. Then our spiritual senses will be exercised. In Ephesians 4:15, we are urged to "speak the truth in love in order to grow up."Notice there the balance between truth and love. Should we speak the truth? Yes. Always. But are we permitted to speak it in any way we like? No. We must speak the truth in love. If you cannot speak the truth in love, then you should wait until you have enough love for people to speak the truth to them. Love is the board on which you can use the pen of truth. If you try to write the truth without a board to write it on, you will be writing in thin air. No-one will be able to understand what you are writing. It is by speaking the truth in love always - in the pulpit and in private conversation - that we can "grow up in all aspects into Him who is the Head, even Christ."
In Ephesians 4:16, Paul speaks of "the whole body, being fitted and held together by what every joint supplies, according to the proper working of each individual part, causing the growth of the body for the building up of itself in love".
The joints here speak of fellowship. Consider how many joints you have in just one arm. There is a joint at the shoulder, another at the elbow, one at the wrist, and then three in each finger - at least 17. It's the joints that make your arm work freely. If you had a strong upper arm and a strong lower arm, but if your elbow was stiff, what could you do with that arm? Nothing. It is not just strength that makes your arm useful. It is also functioning joints. Consider now the application of this to the Body of Christ. Here is a good brother, a strong upper arm. And here is another good brother, a strong lower arm. But they cannot fellowship together with each other. That is the tragedy in the Body of Christ today. In the human body, this is called arthritis and it is very painful. A lot of local churches have arthritis. When our joints function properly, there is no noise. But when a body has arthritis, it creaks and every movement produces an unhealthy noise. What is called "fellowship" among some believers is exactly like that. It creaks. But when the joints function well, there is no noise at all. Our fellowship with each other must be like that. If it is not like that with you, then you need to take some medicine for arthritis: Die to your "self-life". Then you will be healed and your fellowship with others will be glorious. That is the will of God in the Body of Christ.