Here in chapter 18 we find Jesus teaching what I would call drastic measures. First when it comes to sin, if your hand causes sin cut it off, if your eye causes sin gouge it out. Then there is the path to treating a person as you would a tax collector or pagan. Finally there is the unmerciful servant who is shown mercy , then does not show it in return and ends us tortured in prison. Many times I have read this chapter looking for a way to soften the blow, and the reality is there is not must of a way, but that I think is the teaching point.
When it comes to the severing of limbs and removal of eyes, this is one of those places Jesus is not being literal. Yet there is still a powerful charge here. If there is something in your life that is sinful, or generating sin, we must ruthlessly eliminate it from our lives. Even if it seems harmless most of the time, it means elimination. Therefore, if you struggle with say pornography on the computer, it might mean getting rid of the internet. If you struggle with overeating, it is time to have drastically less food around. It is better to sacrifice something we see as important for the sake of our relationship with God, than to be sucked into a life that does not honor God.
With the expulsion of a member of the church. There are times when people are invited to not be a part of a church community. Not a light or easy moment at all. Still when Jesus says treat this person like you would a tax collector or pagan, we must remember who Jesus hung with. Many of Jesus' critics came after him because he was hanging our with tax collectors and pagans. While with them he was calling them to a new life.
Finally the unmerciful servant. We are shown great mercy on a daily basis, do we show it to others? This is one of the more difficult principles of faith to live. It is often easy to receive mercy, but much more difficult to extend it. We are not perfect people, yet we expect perfection from others. Leaving room for our imperfections and others as well is a key to community.
None of these teachings are easy to put into practice in our lives. Still, they are a part of the path to fullness in our lives. May you join the journey.