1 John 3:23, And this is His commandment, that we believe in the name of His Son Jesus Christ and love one another, just as He has commanded us.
This can be called the summary statement of what it means to be Christian—to believe in Christ and love thy neighbour. It sounds simple enough, but it is a loaded commandment; for to believe in Christ is to confess Him as Lord and Saviour, and to confess Him as Lord is to obey His voice, even unto death, just as He died for you; and to confess Him as Saviour is to believe He is the only door to salvation (John 10:9).
Loving thy neighbour flows from Christ’s jurisdiction as Lord and His redemption as Saviour. Loving thy neighbour, therefore, is not approving of heresy and false doctrine in our neighbour’s life, neither does it approve of any sin or idolatry but rather graciously calls them to repentance and to sin no more. These dangers must be opposed lovingly—that is, with compassion, empathy, and longsuffering. We do not “hate the sin but love the sinner” because we end up hating the sinner anyway. Rather, hate the Devil and love the sinner. Again, in doing so we must be compassionate, empathetic, and longsuffering.
As Lutherans, let us not become bloated with our sound doctrine and intellectual self-righteousness that we stop loving our neighbour, as is the habit of some. For as Paul has said, “And if I have prophetic powers, understand all mysteries and all knowledge, and if I have all faith, so as to remove mountains, but have not love, I am nothing” (1 Corinthians 13:2). We might have sound doctrine, but by lording it over our non-Lutheran brothers and sisters in Christ instead of loving them in the jurisdiction and redemption of Christ our Lord and Saviour, we not only become clanging cymbals (v.1), but we also make void the love of Christ, for it is not Lutheranism that saves, but Jesus Christ.