In our passage for study, Jesus reminds his disciples that the Father is passionate about restoring a "little one", a believer who has drifted in the faith, and he invites his disciples to take on a similar divine concern for a brother or sister who has fallen away.
 v12-14. The parable of the Lost Sheep is used in Luke's gospel, along with the parables of the Lost Coin and the Lost Son (the Prodigal Son), to illustrate divine joy for the salvation of a lost sinner, a joy which shapes Jesus' behavior and should have shaped the behavior of the Pharisees in their response toward a converted "sinner", cf. Luke chapter 15. In Matthew's gospel, this story of a sheep-herder's determination to find his lost sheep, serves to illustrate the Father's willingness to go all-out to restore a strayed "little one." The story serves as an invitation to all believers to go out of our way to restore all who have strayed from the family of faith.
v15-17. Matthew now puts together three independent didactic sayings from Jesus which seem to touch on church discipline, yet "discipline" is most likely not the point. Verses 15-17 are often treated as a method for dealing with a brother who has hurt us - sinned against us. The method is constantly used in Christian fellowships with varying degrees of offence. The Revised English Bible follows some of the major texts and leaves out the "against you" of v15. Also, "won ... over" (gained), is best understood in the terms of "restored", cf. 1Pet.3:1. A believer, a "little one", has sinned. The sin is undefined, but the result is that their standing before Christ needs to be restored. Something has undermined their faith and it needs to be sorted. If a single member of the Christian fellowship fails to help the "little one", then two members must try, and if this fails, the fellowship as a whole should apply themselves to restore the strayed member. If the "little one" refuses to listen, then they must be left to their own devices; another unbeliever among the many.
v18. This verse is often used to support the idea that if a Christian fellowship decides something about a brother, whether to accept them or put them out of the church, then this decision is confirmed in heaven. The verse is also used to give weight to the power of a prayer agreed to by a church congregation. Yet, we are most probably dealing with the idea presented in John chapter 20, verses 22-23. The Christian fellowship is authorized to confirm God's forgiveness to a repentant sinner, as well as confirm judgement on a self-righteous rebel.
v19-20. This verse has constantly been used to promote the idea that when two or more Christians believe something in prayer, it will be done for them. As a consequence, many believers have had to wrestle with the problem of unanswered prayer. A more conservative interpretation takes this verse as a promise that when two or three meet in Jesus' name, he will be present, revealing his will to them through the ministry of the Word. The congregation can then pray, believing that it will be "done for" them. Yet, the context pushes toward an even narrower interpretation. The "anything" is most likely the offer of divine forgiveness for all and every sin. Jesus is probably restating v18. When we seek the forgiveness of sins for a brother or sister, in fact, any person broken before God and seeking his love and acceptance, no matter what the sin, then their forgiveness is granted by God. We can be sure of this, for Jesus stands with us on this matter.
 Our passage for study is often used to teach a range of truths. For example: If a believer goes astray the Lord Jesus will abandon his flock to their own devices and go and seek after the one that went astray; If a brother or sister sins against us we should seek them out and remove the speck from their eye and if that doesn't work we should gang up on them; If the church fellowship decides on something, like the purchase of a new carpet, then it is agreed to in heaven; In fact, anything that at least two believers pray for in faith will be granted by God, which, by the way, is why we have major problems with unanswered prayer.
Actually, my father always said that my grandmother had obviously taken to heart the parable of the Lost Sheep, because she went out of her way to look after his wayward brother and hardly gave him a thought. What is Jesus on about in this passage? I take it that Jesus' subject is the divine acceptance and inclusion, through forgiveness, of a lost and wayward soul.
This passage contains a simple message. Our God is passionate for the salvation of lost and wandering humanity and he wants us to be fired by the same passion. When it comes to a brother or sister who has, as it was once called, "fallen from grace", we should be as passionate for their restoration as God is. Some immorality, relationship or intellectual quest has undermined their faith and they have drifted in their reliance upon Christ for their salvation. When this happens, we need to get off our tails and search them out; pull out all stops so that they hear again the grace of God's unconditional forgiveness in Christ. We have the right to confirm to the repentant sinner God's offer to forgive their sins and the privilege to pray for the forgiveness of those who turn to Christ.
 1. Who is the sinful brother and what are we to do with them?
2. Discuss the idea that the sinner we need to speak with is not actually someone who has personally sinned against us.