For if you forgive men when they sin against you, your heavenly Father will also forgive you. But if you do not forgive men their sins, your Father will not forgive your sins.
Just like the verses before this, here is a great challenge.
And also a little bit of a result if you do not forgive.
Bot don't think of this as some kind of curse or threat, think of it as a description. Children of God are forgiving people. And people who do not forgive, are not children of God.