"Be on your guard against false prophets; they come to you looking like sheep on the outside, but on the inside they are really like wild wolves.
You will know them by what they do. Thorn bushes do not bear grapes, and briers do not bear figs. 1
References for Matthew 7:16
A healthy tree bears good fruit, but a poor tree bears bad fruit.
A healthy tree cannot bear bad fruit, and a poor tree cannot bear good fruit.
And any tree that does not bear good fruit is cut down and thrown in the fire. 2
References for Matthew 7:19
So then, you will know the false prophets by what they do. 3
References for Matthew 7:20