A good tree cannot bear bad fruit, nor can a bad tree bear good fruit.
In this passage Jesus continues the previous thought, showing that a person’s nature is inevitably reflected in his deeds. Just as a good tree cannot naturally produce bad fruit, so a devout and honest person cannot do evil, because a good root bears good fruit. In the same way, an evil or hypocritical person cannot practice true goodness or righteousness, because by his nature he is opposed to it. Yet Jesus’ word is not only a judgment, but also a message of hope: a person can become a good tree only by God’s grace. It is that grace that transforms the heart and gives new life. This word reminds us that the believer’s words and deeds must be in harmony with his spiritual nature, and that only from a heart renewed by grace can good fruits be born.