Read: Matthew 18:15-20
"If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. (Matthew 18:15 ESV)
A lot of the language used in describing the early community of Christ followers was familial in nature. Brother and sister were words regularly used to refer to fellow believers. This is the kind of brother Jesus was speaking of.
There will be times in this life in which we find ourselves at odds with fellow believers. Usually it will be a difference of opinion or a misunderstanding, but there are also times when this tension will be a result of a moral failing. We have an obligation to address the sins of those we care about.
Too often in the Christian culture we paint sin as something incredibly easy to deal with, but the truth is that sin is anything but easy. Obviously we are supposed to take our sins before Christ as a matter of repentance and forgiveness. But what about dealing with them friend-to-friend and brother-to-brother?
Jesus advocated one-on-one confrontations. Upfront personal conversations are best. Sitting with someone and talking the issue out always reveals the honest nature of those involved. It cuts through the potential miscommunications and lays all of the cards on the table. Hopefully in a way that brings healing and restoration to the relationship, and points the one who has sinned toward redemption.