…That is, the mystery which has been hidden from the past ages and generations, but has now been manifested to His saints, to whom God willed to make known what is the riches of the glory of this mystery among the Gentiles, which is Christ in you, the hope of glory. We proclaim Him, admonishing every man and teaching every man with all wisdom, so that we may present every man complete in Christ.
— Colossians 1:26-28
As an example of how to admonish and teach the saints, take the case of a brother who falls in love with an unbeliever. The serving one has to warn him, “Brother, we are not God, and we cannot tell you whom to marry. But we can tell you that, according to the principle in the Bible, we should not become unequally yoked by marrying someone who is not a fellow believer.”
To teach, admonish, and warn the saints so that they may grow in a healthy way is a suffering. If we do not know how to suffer for the saints in this way, they may only become good churchgoers. Saints will not be perfected if you do not know how to fulfill the word of God and fill up that which is lacking of the afflictions of Christ for His Body’s sake. If you desire Christ to be the reality of the church as its oneness, you must practice such a life.