21 “For it is from within, out of a person’s heart, that evil thoughts come—sexual immorality, theft, murder, 22 adultery, greed, malice, deceit, lewdness, envy, slander, arrogance and folly. 23 All these evils come from inside and defile a person.”
-Mark 7:21-23, NIV
A typical response from some folks about cheating is treating as a symptom of marriage problems. That is a spiritual misdiagnosis, though.
Sure, the affair(s) is a symptom:
It is a symptom of the wickedness in the Cheater’s heart.
This is what Jesus teaches us in Mark 7. The cheating is a sin, of course. This sin reveals a much deeper problem. The heart of the Cheater is given over to wickedness.
A truly Christian, wise counselor understands this and refuses the worldly wisdom of blaming the marriage relationship for the Cheater’s sins.
They understand the focus needs to be upon repentance by the Cheater and the uprooting of the sin within their heart. The marriage stands no chance without this important spiritual work.
I would argue that the Cheater stands in great spiritual peril without confronting their sin and changing their ways (see Hebrews 10:26-27). Too often, well-meaning pastors will focus on “communication” instead of doing this uncomfortable work of dealing with the Cheater’s sins.
So, fine. If you must call the affair a “symptom,” be sure you get the diagnosis of its origin correctly:
It is a symptom of the Cheater’s heart, which is filled with sin.
It always amazes me that of all those sins listed that the only one “Christians” exempt is the sin of adultery.