Matthew 18:15-20  Jesus was teaching His disciples about greatness in the Kingdom.. He taught that it is not the amount of influence, power, or prominence that counts in His Kingdom.. but it is a matter of humble child-like trust and service that means the most to the Father. The "Son of man has come to save that which is lost.. " That is the focus of kingdom ministry. ".. it is not the will of the Father who is in heaven that one of these little ones perish.. "  That is the heart and purpose  of the Father. 

The same heart and purpose also carries over into relationships within the church family.  We are not to be stumbling blocks.. not to be offensive in our actions towards one another.  This especially applies to situations like we find in verses 15-17.. when a fellow Christian is guilty of sinful behavior.... Jesus tells us exactly what to do!

The first step is a private discussion....with love and grace.. for the purpose of restoring your brother or sister. 

If that fails.. then 2-3 witnesses are to meet with that brother or sister.  These are "witnesses".. not hear-sayers.. not those who have been told unconfirmed rumors..  but loving, caring, spiritually mature christians who care about the restoration of the one who is guilty of sin. 

And if that does not bring changes.. then the whole church is involved. If this person cares at all about the Body of Christ, this should be enough to bring about repentance and restoration.  If not.. they must leave the fellowship.  

Again, the whole teaching is God's plan for His Kingdom people.. the sinner is a "stumbling block" that could cause others to stumble.. it is better that they be "cut off" than to offend and cause "one of these little ones to perish." 

Again, Jesus talks about this idea of "binding" and "loosing". He spoke about this in Matthew 16:19.. in the context of the church and the "keys of the kingdom of heaven".  The Bible Dictionary says that "Heaven sets the standard and earth follows heaven's lead" in this matter.  What we do.. as the Church.. must follow the heart and purpose of Heaven.  That is why it is so important that there is agreement.. in prayer.. asking the Father's will in these matters.  It is why we are "gathered together" in His Name.. where He is in our midst.  These decisions have eternal consequences.. 

Father  in heaven, we have often failed to handle discipline within the church in Your ways. Forgive us. We have failed to show love and compassion.. we have failed to forgive and restore our fellow believers. We have been stumbling blocks.. we have offended.. we have caused others to stumble.. please forgive us.  Lead us, Holy Spirit, to be living sacrifices.. acceptable to You.. transformed by You.. renewed in our thinking by Your Word. May we not think "more highly of [ourselves] than [we] ought to think.. " ( Romans 12:1-3). But, may we love "without hypocrisy" and "be devoted to one another in brotherly love.. devoted to prayer.." and overcoming evil with good.  Let Christ be seen in us.  Abide in us Jesus, working all things in us that are well-pleasing to the Father.  We ask this in Your Name. Amen.