Relationships matter to God. Our relationships with one another effect not only our relationship with but also our worship of our Creator. Unity and purity must be preserved and unreconciled differences and sin are a ticking time bomb.
Therefore if you are presenting your offering at the altar, and there remember that your brother has something against you, leave your offering there before the altar and go; first be reconciled to your brother, and then come and present your offering. -Matthew 5:23-24
In context, being angry with your brother can have both legal and eternal consequences. Jesus urges His hearers to fix the issues before they are beyond repair. Later in Matthew, He gives this command specifically regarding sin with a two-fold aim: unity and purity.
If your brother sins [against you], go and show him his fault in private; if he listens to you, you have won your brother. But if he does not listen to you, take one or two more with you, so that BY THE MOUTH OF TWO OR THREE WITNESSES EVERY FACT MAY BE CONFIRMED. If he refuses to listen to them, tell it to the church; and if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector. -Matthew 18:15-17
The offense is not allowed to go ignored if it is garnering hurt feelings or ill-will especially if sin is the issue. The goal of the sought after reconciliation is unity within the Body. After all, contention has the potential to breed further widespread discord which can splinter groups into factions. Jesus’ process for preservation begins with a 1-on-1 confrontation in private. There is no need to air dirty laundry. Only after the offender refuses to listen are others brought in for aid beginning with only 1 or 2 then finally escalating to the church’s intercession. If the person is unwilling to respond to all of these attempts, they simply do not want to be reconciled.
However unity is not the only goal Jesus has in mind. The other aim, and possibly the primary one, concerns the purity of the Body of Christ. If a person witnesses someone sinning and says nothing, they are condoning the sin. This will eventually infect the church. We see an example of this in 1 Corinthians 5. The whole Corinthian church seemed to know about the man’s inappropriate relationship with his father’s wife. Yet Paul indicated that none of them did anything about this sin. Paul asks them, “Do you not know that a little leaven leavens the whole lump of dough?” (5:6)
Jesus deals with two types of confrontation-your brother having something against you and witnessing your brother sinning-the basis of both is love. We want reconciliation and unity with our fellow Christians because we love God’s Family. We want purity within every Christian’s life because we love them. Therefore we want our brother or sister to stop sinning so they will be pleasing to God.
Unity and purity are extremely important. The way we treat one another matters. Unreconciled differences and especially sin cannot be allowed to get in the way. The price Jesus paid was too steep to permit the church to splinter because of unchecked dissension.