By their fruit you will recognize them. Do people pick grapes from thornbushes, or figs from thistles? Likewise every good tree bears good fruit, but a bad tree bears bad fruit. A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit. Every tree that does not bear good fruit is cut down and thrown into the fire. Thus, by their fruit you will recognize them.
Jesus is first and foremost warning about wolves in sheep’s clothing who fool Christians into believing that they are genuine. This is a valid lesson for every Christian however.
There are many people who have been taught to say the right things and can put up a good front. The Christian who is just looking at the surface can be fooled into believing that they are genuine believers.
The truth is that anyone can do good things. Even the most immoral person is capable of writing a check to support a cause they like or to gain a tax write-off. Their true colors will be shown if they are observed closely however because they can’t keep up the front forever. A bad tree will bear bad fruit.
Genuine Christians can’t help but bear good fruit however. It is not a matter of choice. Christians will naturally bear good fruit without thinking about it because it is a part of their nature. Just as a fruit tree can’t decide that it is going to stop bearing fruit, so a genuine Christian can’t help but continue to bear good fruit.
Because a Christian has had their life changed by Jesus Christ they are a new person. The old, bad fruit will decrease as they mature in Christ. Soon they will bear more and more good fruit – a sign of their maturity.