True relationships require mutual understanding and respect.  People working in the same business need to share common values: families cannot hold together unless they choose to love each other.  Jesus had just commanded the disciples to be merciful, because that is how our Heavenly Father operates (Luke 6:35).  Mercy is part of the 'family value system' of heaven; it is essential to Christian faith.  Those who receive mercy must show mercy.

Jesus was warning the disciples that hypocrisy in this area is unacceptable to Father God.  The spiritual leaders of His day were good at making up rules to catch people out and condemn them.  Indeed, religion based on rules will always end up being hypocritical, because even the religious leaders cannot keep them all.  But Jesus came to show a totally different way of being in favour with God - a way that is open to everyone: trusting God for mercy because of Christ's death and resurrection.  So those who have escaped judgement should stop accusing others.  And how can those who rejoice that their condemnation was placed on Jesus, condemn others (James 2:8-11) ?

Of course, at this stage in His ministry, Jesus had not yet died for sins, nor had the Holy Spirit been given to the church. But this was the disciples' training course to become apostles.  They were learning the principles which needed to be taught in the church for many years until Jesus returned.  Peter must have remembered because he wrote, ‘Above all, love each other deeply, because love covers over a multitude of sins.’ (1 Peter 4:8).

The principle of forgiveness is contrary to our fleshly nature but totally consistent with God's nature.  It is the antidote to the poison of bitterness, and the window of hope to those trapped by evil.  To put this into practice today, identify somebody you have to work with or see often, who is out of order: pray for that person and choose not to resent them and positively show kindness to them.  Where you have been wronged, forgive (Genesis 50:17).