Fruit of all kinds including figs, olives and grapes - grown on trees and vines - have been the mainstay of the Mediterranean economy for centuries. Of course, a diseased tree will hardly support any fruit, while a healthy tree always promises a good crop in a predictable climate.  Everybody listening to Jesus knew that the type and variety of fruit depended on the nature of the tree or vine, so He used this illustration to show that people behave according to what is in their heart.  Wickedness comes out of evil hearts (Hosea 10:13) and graciousness out of sanctified hearts.

In training the disciples for their future role as church leaders, Jesus needed to emphasise the radical difference between His Kingdom and religion.  Religious people can be sincere, informed and socially helpful; but the nature of their hearts is not changed by their indoctrination (Jeremiah 9:8).  Our worst excesses may be restrained by rules, but love does not naturally come out of hate any more than grapes come from briars.  Caught off-guard, we say what we really mean.

Jesus is recorded as taking this further in Matthew 12:34-37, when speaking to the religious leaders: ‘You brood of vipers, how can you who are evil say anything good? For the mouth speaks what the heart is full of. A good man brings good things out of the good stored up in him, and an evil man brings evil things out of the evil stored up in him. But I tell you that everyone will have to give account on the day of judgment for every empty word they have spoken. For by your words you will be acquitted, and by your words you will be condemned.’  This is not just a matter of learning to be more disciplined, but needing a new heart.  It is not a matter of social improvement but of eternal destiny.  Only those who long to be like Jesus will ask for Him to give them a new heart (Ezekiel 11:19).

It is certainly important to practise the disciplines which will lubricate the life of Christ flowing through us to others.  But those disciplines alone will never make us holy.  Only God can change our nature, by His Spirit, as we submit to the Lordship of Jesus Christ.  People who are trusting Jesus alone are willing to receive a heart like His; one which will love righteousness, hate wickedness, respond to God's call, receive His grace and serve Him sacrificially with gladness (Psalm 51:10).  That sort of person is a breath of fresh air in the workplace: they provide a glimpse of heaven in legal practice, public service, commerce, art, healthcare or education.  So, if you belong to Jesus, ask Him to change your deepest desires to be like His.  Then His life will flow through you to bless many around you.