Lying lips are abomination to the LORD: but they that deal truly are his delight.
-Proverbs 12:22, KJV
Liars lie. And cheaters by the fact that they cheated are liars. A wise person does not just take them at their word.
Words need to be verified by action.
I do not recommend trusting a cheater to appropriately break off an affair on their own. It is like trusting an alcoholic to get rid of all his bottle stashes. Unwise.
This break off could happen in writing, over the phone, or in person. It ought to be direct, not unkind, but crystal clear that the relationship was inappropriate and is now forever over.
No, remaining friends with the affair partner is not an option!
This person posses an existential threat to the marriage. Staying connected to them is like playing Russian Roulette:
Some days may be innocent, but one day you’ll find the chamber with the bullet, and it will be all over in the messiest of ways!
It is best to insist on putting the “gun” down.
And for the manipulative cheater types, this boundary has nothing to do with allowing or not allowing a cheater to have friends.
-The reason this person is off limits is not because they are simply another person. They are off limits because you cheated with them.
-Presumably, there are plenty of other people in the world with whom you haven’t cheated and with whom, thereby, you may be friends. This is just one person who doesn’t fit that description.
I made the mistake of allowing my (now ex) wife break off an emotionally and romantically inappropriate relationship alone. She played on my sympathy and Christian charity to do this.
The lines I remember hearing where about how this relationship only became inappropriate because she led it there.
I now recognize a pattern where she was more concerned about hurting this affair partner than how she had hurt her husband by cheating.
Don’t get played like me.
It perfectly reasonable to expect an inappropriate relationship to be terminated regardless of who initiated it. That does not change the reality that it was inappropriate.
And do not leave this task to the cheater to accomplish without your oversight. They have already demonstrated by their behavior that they prioritize this relationship over your marriage.
So, you shouldn’t be surprised if they do a less than complete break with this person when left to their own devices.
Yet, I do believe this can be done in direct and kind manner. The affair partner does not need to be abused verbally in the terminating communication.
However–speaking as a pastor here, not a therapist–they need to be reminded that the relationship was inappropriate, and that they wronged the faithful spouse. If they are Christian, then I think it is perfectly appropriate to call this sin, sin.
“John, I am calling today with my husband to inform you why I will no longer be in contact with you.
We both know our relationship crossed over into inappropriateness for married people. I seriously abused the trust of my husband in how I related to you. Because I did this, I can no longer be friends with you, and this will be our last communication.
Please do not try to contact me. Good-bye.”