Church discipline has at least five purposes. First, discipline aims to expose. Sin, like cancer, loves to hide. Discipline exposes the cancer so that it might be cut out quickly (see 1 Cor. 5:2).
Second, discipline aims to warn. A church does not enact God’s judgment through discipline. Rather, it stages a small play that pictures the great judgment to come (1 Cor. 5:5).
Third, it aims to save. Churches pursue discipline when they see a member taking the path toward death, and none of their pleading and arm waving causes the person to turn around. It’s a device of last resort (1 Cor. 5:5).
Fourth, discipline aims to protect. Just as cancer spreads from one cell to another, so sin quickly spreads from one person to another (1 Cor. 5:6).
Fifth, it aims to present a good witness for Jesus. Church discipline, strange to say, is actually good for non-Christians, because it helps to preserve the attractiveness of God’s people (see 1 Cor. 5:1). Churches, remember, are to be salt and light. “But if the salt loses its saltiness,” Jesus said, “it is no longer good for anything, except to thrown out and trampled underfoot” (Matt. 5:13).
…The underlying purpose in every act of discipline, of course, must be love: love for the individual, love for the church, love for the watching world, love for Christ.
God, after all, “disciplines the one he loves”; and “he chastens everyone he accepts as his son” (Heb. 12:6). By abstaining from discipline, we claim that we love better than God.
God lovingly knows that discipline yields life, growth, and health: “God disciplines us for our good, in order that we may share in his holiness” (Heb. 12:10). Yes, it’s painful, but it pays off: “No discipline seems pleasant at the time, but painful. Later on, however, it produces a harvest of righteousness and peace for those who have been trained by it” (Heb. 12:11).
Jonathan Leeman, Church Membership: How the World Knows Who Represents Jesus, p. 110-111