The main point of contention between the Amish and the Anabaptists involved the exercise of Meidung, which translates as to shun or excommunicate. The Anabaptist faith maintains that only the pure should be involved in religion; if any member were to fall into sinful action, he should be excommunicated and shunned. The latter custom is based on the discipline of fellow believers as described in Matthew 18:15-17:
Moreover if thy brother shall trespass against thee, go and tell him his fault between thee and tell him alone...But if he will not hear thee, then take with thee one or two more...And if he shall neglect to hear them, then tell it onto the church: but if he neglect to hear the church, let him be unto thee as a heathen man and a publican.A non-conforming member would be ostracized; the community of believers would terminate all contact with him. Amman took this practice one step further and required the spouse of a person under the ban to neither sleep nor eat with them, until the heretic repented and changed his behavior or beliefs. Additionally, he advocated shunning all members that leave the Amish church and those who marry outsiders. He also mandated that no Amish should buy from, sell to, or even eat at the same table as the excommunicated individual. These traditions, passed down from generation to generation, have kept the Amish way of life stable.
from The "Plain Folk": The Amish and Mennonites
http://www.amishinfo.com/amish/amishinfo.html#meidung
