When God saw what they did and how they turned from their evil ways, he relented and did not bring on them the destruction he had threatened.
– Jonah 3:10, NIV
To advert absolute destruction by God, the Ninevites repented and God mercifully relented from carrying out His judgment upon them.
This is the clear pattern of forgiveness here. Repentance is required. This is true–maybe especially so–when MUCH is forgiven as in the case of the wicked Ninevites.
We ought not to lower God’s standards for repentance when dealing with cheaters.
When a cheater suggests he or she is forgiven by God for their lies, abuse, and infidelity, that ought to beg the question of what did they do to repent?
If the answer is little to nothing, then that ought to tell a godly Christian that the cheater is probably not forgiven by God. God requires repentance (see Hebrews 10:26-27, I John 3:6, etc).
Insisting on repentance isn’t mean or cruel. It is godly.
Such an insistence is actually kind as it encourages the cheater to escape coming judgment before it is too late in the next life (2 Corinthians 5:10).
This pattern of requiring repentance isn’t “just” an Old Testament thing either. Jesus explicitly references this story as a model to be followed (see Matthew 12:38ff).
Clearly, Jesus taught repentance as important for those who are truly part of his family!
*A version of this post ran previously.