21 Then Peter came to Jesus and asked, “Lord, how many times shall I forgive my brother or sister who sins against me? Up to seven times?”
22 Jesus answered, “I tell you, not seven times, but seventy-seven times.
Matthew 18:21-22
In this article on Matthew 18, Peter’s question about forgiveness was extremely generous. Imagine his shock when Jesus replies with such an outlandish response. This kind of forgiveness is not a normal human response to the offending words or behavior of another person.
Normal human behavior is detailed for us in Genesis 4 at the beginning. The familiar story of Cain and Abel demonstrates the powerful emotion of anger and resentment.
FAULTY THINKING
Here, in Genesis 4:1-16 Cain’s sacrifices to God were not acceptable while Abel’s were welcomed by God. Abel had sacrificed from his “firstborn” of his flock of sheep in faith that God would provide for the future. Conversely, Cain sacrificed “some of the fruits of the soil” rather than from the firstfruits (vss. 3-5).
A logical response would be for Cain to do what was required to make his sacrifices acceptable to God. Rather than correcting his behavior Cain chose to become angry with his brother (vs. 5) to the point that he attracted God’s attention. God counseled to Cain:
“Why are you angry? Why is your face downcast? If you do what is right, will you not be accepted? But if you do not do what is right, sin is crouching at your door; it desires to have you, but you must rule over it” (vss. 6-7).
MURDEROUS INTENT
Cain’s response was to lure his trusting brother into a field. There, Cain’s anger had consumed him to the point that the only solution 
he could see for his failure was to murder Abel. God’s conversation with Cain is enough to strike fear into the heart of anyone whose sin has been revealed:
9 Then the Lord said to Cain, “Where is your brother Abel?”
“I don’t know,” he replied. “Am I my brother’s keeper?”
10 The Lord said, “What have you done?” (vss. 9-10)
Continuing, God judges, convicts and sentences Cain:
Listen! Your brother’s blood cries out to me from the ground. Now you are under a curse and driven from the ground, which opened its mouth to receive your brother’s blood from your hand. When you work the ground, it will no longer yield its crops for you. You will be a restless wanderer on the earth” (vss. 10-12).
CONSEQUENCES WITH A PROMISE
When Cain complains in fear of the consequences of his sentence–which would be that he suffer the same fate of his brother–God responds with a promise: “…anyone who kills Cain will suffer vengeance seven times over” (vs. 15).
GENERATIONAL CURSE
In Genesis 4:17-24, seven generations after Adam and Eve through Cain’s descendants, we are briefly introduced to Lamech who brags 
to his two wives:
“I have killed a man for wounding me,
a young man for injuring me.
If Cain is avenged seven times,
then Lamech seventy-seven times” (vss. 23-24).
Cain’s murderous rage at his brother began with a perceived injustice that festered from one generation to the next. Lemech represents the darker side of the family trait of rage as it blows past simple revenge and an “eye for an eye” sort-of justice to an extreme that knows no limits. Crushing vengeance that destroys others over the slightest offense to make sure they suffer beyond measure.
The trend in Cain’s death spiral genealogy would finally meet its termination in Lamech’s son of whom he would predict: “He will comfort us in the labor and painful toil of our hands caused by the ground the Lord has cursed” *Genesis 5:29). Lemech named his son, Noah.
LAMECH’S SON: THE END OF JUSTICE BEYOND MEASURE
One reference to those perilous times by Peter’s question would elicit a 3-dimentional response from Jesus that would be driven home by The Parable of the Unmerciful Servant.
This powerful ending to Matthew 18, a significant chapter on conflict resolution and forgiveness, would conclude with Jesus’ assertion that citizens of the kingdom of heaven must “forgive your brother or sister from your heart” (vs. 35). We will address this parable and Jesus’ conclusion in the final article of this series on Forgiveness and Matthew 18.