No good tree bears bad fruit. No bad tree bears good fruit.
Know each tree by the fruit it bears. You will not see people get figs from thornbushes, or grapes from brambles.
Good people bring good things out of the good treasure of their heart. Evil people brings evil things out of the evil treasure of their heart.
And as the heart overflows, the mouth speaks.
(Matthew 7:15-23; Matthew 12:33-37)