In the story of the Unforgiving Servant, we learn an important lesson. The person who has forgiven is the one who will be forgiven. Conversely, the person who has not forgiven is the one who will not be forgiven. Jesus tells the rest of the story in Matthew 18.
28 But when that same servant went out, he found one of his fellow servants who owed him a hundred denarii, and seizing him, he began to choke him, saying, ‘Pay what you owe.’
29 So his fellow servant fell down and pleaded with him, ‘Have patience with me, and I will pay you.’
30 He refused and went and put him in prison until he should pay the debt.
31 When his fellow servants saw what had taken place, they were greatly distressed, and they went and reported to their master all that had taken place.
32 Then his master summoned him and said to him, ‘You wicked servant! I forgave you all that debt because you pleaded with me.
33 And should not you have had mercy on your fellow servant, as I had mercy on you?’
34 And in anger his master delivered him to the jailers, until he should pay all his debt.
35 So also my heavenly Father will do to every one of you, if you do not forgive your brother from your heart.”
Again, the one who has not forgiven is he who will not be forgiven. Conversely, the one who has forgiven is he who will be forgiven. Thus, we ask God to forgive us our sins, as we have forgiven others. For as we have forgiven others, God also shall forgive us.
That is why Jesus said in vv. 14-15, “For if you forgive others their trespasses, your heavenly Father will also forgive you, but if you do not forgive others their trespasses, neither will your Father forgive your trespasses.” Connecting v. 12 with vv. 14-15, we come to this conclusion. We ask God to forgive us our debts. But before that, we must forgive our debtors first. We will be forgiven as we have forgiven others. As we have not forgiven others, then we will not be forgiven.
That is the point of Jesus in vv. 14-15. The person who has not forgiven others shall not be forgiven also. But the person who has forgiven others shall also be forgiven.
Thus, we ask God to forgive us our debts, just as we have forgiven our debtors. God shall forgive us, as we have forgiven others.