Speaking the truth, in love, is essential to the spiritual growth of the body. This Greek word alēthēs translated here as “truth” means 'to not conceal or hide something; to not hold back or keep to yourself.' So Paul is telling us that an open-hearted sharing with one another is vital to spiritual growth. Many today teach that love between the brethren means that we keep quiet or that we do not see what is wrong. But that is a false unbiblical teaching. An honest sharing of the heart, governed by agape "love", (which is God's love), is vital. Love does not place its blessing on iniquity or sin in the church, neither does it turn a blind eye, but rather it "rejoiceth in the truth" (I Cor.13:6).
But we are told in I Peter 4:8 that "charity shall cover the multitude of sins" in other words keep them secret. How do we reconcile these two statements? The answer is that the love of God governs both. Both statements are united and agree in the fact that they both concern dealing with your brother on a personal basis. You go to him and speak honestly and openly in love, maybe pointing out something in his life that will harm him or hinder him in his walk with God. But the very same love covers or hides these sins from the public gaze when dealt with privately and scripturally. Someone who rejects such loving correction generally leaves themselves open to public reproach for their undealt with sins. The man who says that because of love he will not deal with his brother is actually not acting in love; he is denying it and not allowing it to flow. Love compels you to speak. But on the other side the man who speaks what is true but without love which operates in and through meekness, carefullness, wisdom and privacy is wrong.
Thus speaking the truth in love is a wonderful protection to the individual and to the body of Christ. Anyone who teaches that because of love we must not, should not, cannot deal with issues in our brothers life is denying the healthy function God has ordained for the local church.