Do you know why you are supposed to forgive others? Matthew 5-7

Matthew 6:14-15 (NASBStr)

For if you forgive others for their transgressions, your heavenly Father will also forgive you. But if you do not forgive others, then your Father will not forgive your transgressions.

It might be tempted to believe that the above passage teaches something it does not.   To the casual reader and less focused, the above passage might sound as if Jesus is postulating the thought that "if you want your sins to be forgiven, start by forgiving others."    There area few major denominations that foster that same belief and this is their proof text.   They would maintain that God waits to see if we forgive others before He, in turn, forgives us.  The problem with that thought is that in contradicts all other passages in the Bible that state our forgiveness is not a matter or works but faith (Ephesians 2:8-10; 

Romans 3:27-28).  So, if that is what it does not mean, what does it mean?  Jesus adds another passage that emphasizes the same thought in Matthew 18:23-35 when He tells the story about the man who forgave one of his debtors a great debt and the same man went out and wouldn't forgive one of his own debtors a small debt.   Christ's point here is that if we have, indeed, come to know the forgiveness of God, through faith in Christ, how can we ever not forgive others?  Any debt others have incurred against us is minuscule compared to the debt we have accumulated toward God.   Note what the following commentary says about this same passage before us:

Word Biblical Commentary:  "It is clear from these verses that a direct connection exists between God's forgiveness and our forgiveness. But it is a given that God's forgiveness is always prior (Matthew 18:23- 35). These verses are a forceful way of making the significant point that it is unthinkable- impossible- that we can enjoy God's forgiveness without in turn extending our forgiveness toward others. Paul makes use of this logic in Col 3:13."

Colossians 3:13 (NASBStr)

bearing with one another, and forgiving each other, whoever has a complaint against anyone; just as the Lord forgave you, so also should you.

Jesus point, above, and in the parable, along with Paul's words, are to express one giant point for us: We have no business holding wrath toward someone when God has forgiven us of such a great debt.   We need to remember that God went to great lengths to pay our debt, by sending His Son, Jesus, to pay it by His life.   With that said, we should note that means that the wrong others have done against us is not simply forgotten as though it was not important, or didn't matter.  It is paid for.   That means someone already suffered for the debt: Jesus.   So, I can forgive someone for the wrong they did against me because the punishment they deserve was poured out on Jesus.  So, I not only forgive them because God has forgiven me, but also, I can forgive them because their punishment has been inflicted on someone taking their place.   So, the above words of Jesus don't say forgive SO you can be forgiven.  They rather say forgive because you have been forgiven.