Matthew 12:33

Either make the tree good, and its fruit good; or make the tree corrupt, and its fruit corrupt: for the tree is known by its fruit.

Dummelow's paraphrase on this passage brings the meaning into sharp focus:

Pharisees, be logical. You say that to cast out devils is good, but that I who do it am corrupt. That is as if you said, The fruit of this tree is good, but the tree itself is corrupt. Make up your minds which way you will have it. Either say that my works are good, and therefore that I am good also, or else that my works are corrupt, and that therefore I am corrupt also. You cannot separate a tree from its fruit, for a tree is known by its fruit. Nor can you separate a man from his works, for he is known by them.[9]