1 Samuel 24:13

You can tell them by their fruit. Do people pick grapes off thorns, or figs off thistles?

So you can tell them by their fruit.

"You must either make the tree sound and its fruit sound, or make the tree bad and its fruit bad; a tree is judged by its fruit.

For out of the heart come wicked designs, murder, adultery, immorality, stealing, false witness, impious speech.

Treasury of Scripture Knowledge

As saith the proverb of the ancients, Wickedness proceedeth from the wicked: but mine hand shall not be upon thee.

You can tell them by their fruit. Do people pick grapes off thorns, or figs off thistles?

"You must either make the tree sound and its fruit sound, or make the tree bad and its fruit bad; a tree is judged by its fruit.

For out of the heart come wicked designs, murder, adultery, immorality, stealing, false witness, impious speech.

But the things that come out of the mouth come from the heart, and they pollute a man.