Most people know that to cheat on your husband and wife is considered a sin from the theological viewpoint. However, it really goes a lot deeper than that. According to Jesus, infidelity starts long before any physical act, and is not just limited to the physical act. Moreover, his standards on fidelity set the bar a lot higher than just not cheating on your husband or wife.
I’ll explain. During his time on earth, Jesus went to great effort to convince people that being a true Christian was more than just following a set of rules. This is evident in almost everything he said, but I’ll use as an example these excerpts from his famous Sermon on the Mount:
“You heard that it was said to those of ancient times, ‘you must not murder; but whoever commits a murder will be accountable to the court of justice.’ However I say to you that everyone who continues wrathful with his brother will be accountable to the court of justice…” (Matt 5:21-22)
The principle here is that Christians need to condition their hearts before any event potentially leading to sin ever comes along- they must work on shedding any anger or hatred that they harbor and develop peace and love within their hearts. This way, at times of trial, they will avoid sin because their deeply held beliefs have changed them from the inside out- not because they’ve successfully followed the “rules” by suppressing the murderous impulses in their heart.
Likewise, in verse 27: