Matthew 6:15
But if you do not forgive others their trespasses, neither will your Father forgive your trespasses. The negative statement of the same truth: unforgiveness blocks forgiveness. Mark 11:25 records the same warning in the context of prayer: if you have anything against anyone, forgive, so that your Father may forgive you. The connection is not mechanical but organic: the person who cannot forgive has not understood or received the forgiveness they claim. They are the unforgiving servant of Matthew 18, who received an enormous debt-cancellation and then strangled a fellow servant over a small debt — the failure of forgiveness reveals that the prior forgiveness was never truly received.