Matthew 18:16

“But if he does not listen to you, take with you one or two more, that at the mouth of two witnesses or three every word may be established.”

That the sin is to be seen as something serious comes out here. It is not just a matter of personal disagreement, for now others are to be involved, and they will of course ‘judge' the matter for themselves in order that they might be of help to the one who has fallen. They may in fact in some cases simply advise that in their view the matter is not important enough to take further. But where the sin is a serious one then they will decide on the matter between them and then come to their brother disciple in order to resolve the issue. Note again that the aim is to restore the disciple and to prevent the matter becoming too public. Mercy and forgiveness is ever in mind. Bringing in one or two more (of the kind of character that Jesus has previously described) will ensure that the matter is being fairly dealt with, and the hope is that together they can restore the erring disciple in a spirit of love and humility, without widespread publicity. In this emphasis we discover Jesus' hatred of ‘gossips'.

And as they consider their approach to the one who has ‘fallen' they will pray together. And when these two or three gather together in His Name they know that He will be among them (Matthew 18:20). He will guide them in their thinking and in their approach (compare 1 Corinthians 5:4). And it is only then that they will approach their fellow disciple.

The point here is that now the principle of someone not being judged ‘except on the evidence of two or three witnesses' is in mind (Deuteronomy 19:15). No one should suffer the humiliation of being brought before the whole congregation without the agreement of such witnesses. Clearly therefore they will require some kind of evidence before they can become ‘witnesses'. That could be the evidence of the disciple's own admission of the sin, or some other kind of good evidence. They must ‘enquire, and make search and ask diligently', for without that they would have to reject the charge (compare Deuteronomy 13:14). And Matthew 18:19 emphasises that their judgment must be made prayerfully, and that Jesus' Father in Heaven should be brought in to the matter. For He is the final judge of all men (Matthew 7:23; Matthew 10:32).