‘Moreover’ connects this instruction with what comes before, but what is the connection? He has been warning the disciples against doing anything to harm another believer. To do so is to provoke the Father’s jealous care for his own.
One way we can mishandle offences is to do nothing about them, but to let them grow in our minds. They are not so small that we can simply pass over them, but nor will we let them go. We have a duty to influence one another, to admonish one another over serious matter. If we leave it too long, then when we do finally act, we do so vindictively, because we have allowed offences to grow too big.
This can happen in the marriage relationship. A Christian couple can find themselves thinking things which they are horrified of later. The resolving of disputes extends to all our relationships, but marriage shows us how we should behave. Outside marriage, an offence is committed, and it grows and we detest each other, and are therefore not prepared to do anything about it. We take ourselves much too seriously. In marriage you cannot do this; you know you must restore the relationship. There is a sanction on you from the Lord. You cannot go too far before the Saviour. If we let the dispute grow, no one can convince us it is not as enormous as we think. In church we can get others to help us get disputes growing; not in marriage. We may get hold of a sympathetic friend who is going to take our side, and rope in a third or fourth party. No, says Christ. Go and tell him his fault. Not to attack him, but to win him.
Some things are so minor that we simply overlook them. Christ is not encouraging us to hold out on each other over every little annoyance that we suffer. We must learn to forgive small matters and just move on. What he speaks of here is something serious enough to warrant excommunication, and the New Testament tells us what things fall into that category.
Offences are not the only problem. We need to exhort each other at times also. There are things we ought to be doing as a local church in a more vigorous way and we need to remind each other of this. Offences between people are only one of a number of issues in the local church that require admonition.