Genesis 4:13-24 (New Revised Standard Version)
Cain said to the Lord, "My punishment is greater than I can bear! Today you have driven me away from the soil, and I shall be hidden from your face; I shall be a fugitive and a wanderer on the earth, and anyone who meets me may kill me." Then the Lord said to him, "Not so! Whoever kills Cain will suffer a sevenfold vengeance." And the Lord put a mark on Cain, so that no one who came upon him would kill him. Then Cain went away from the presence of the Lord, and settled in the land of Nod, east of Eden. Cain knew his wife, and she conceived and bore Enoch; and he built a city, and named it Enoch after his son Enoch. To Enoch was born Irad; and Irad was the father of Mehujael, and Mehujael the father of Methushael, and Methushael the father of Lamech. Lamech took two wives; the name of the one was Adah, and the name of the other Zillah. Adah bore Jabal; he was the ancestor of those who live in tents and have livestock. His brother's name was Jubal; he was the ancestor of all those who play the lyre and pipe. Zillah bore Tubal-cain, who made all kinds of bronze and iron tools. The sister of Tubal-cain was Naamah. Lamech said to his wives: "Adah and Zillah, hear my voice; you wives of Lamech, listen to what I say: I have killed a man for wounding me, a young man for striking me. If Cain is avenged sevenfold, truly Lamech seventy-sevenfold."
Matthew 18:21-35 (New Revised Standard Version)
Then Peter came and said to him, "Lord, if another member of the church sins against me, how often should I forgive? As many as seven times?" Jesus said to him, "Not seven times, but, I tell you, seventy-seven times. For this reason the kingdom of heaven may be compared to a king who wished to settle accounts with his slaves. When he began the reckoning, one who owed him ten thousand talents was brought to him; and, as he could not pay, his lord ordered him to be sold, together with his wife and children and all his possessions, and payment to be made. So the slave fell on his knees before him, saying, 'Have patience with me, and I will pay you everything.' And out of pity for him, the lord of that slave released him and forgave him the debt. But that same slave, as he went out, came upon one of his fellow slaves who owed him a hundred denarii; and seizing him by the throat, he said, 'Pay what you owe.' Then his fellow slave fell down and pleaded with him, 'Have patience with me, and I will pay you.' But he refused; then he went and threw him into prison until he would pay the debt. When his fellow slaves saw what had happened, they were greatly distressed, and they went and reported to their lord all that had taken place. Then his lord summoned him and said to him, 'You wicked slave! I forgave you all that debt because you pleaded with me. Should you not have had mercy on your fellow slave, as I had mercy on you?' And in anger his lord handed him over to be tortured until he would pay his entire debt. So my heavenly Father will also do to every one of you, if you do not forgive your brother or sister from your heart."