Translation
Either make a tree good and its fruit [will be] good, or make a tree bad and it fruit [will be] bad; by the fruit, the tree is known.
Paraphrase
On one hand, if a tree is caused to be a pleasing and beneficial tree, then the natural product of that condition will be fruit that is pleasing to eat; on the other hand, if a tree is caused to not be pleasing and beneficial, then the natural result of that condition will be fruit that is unpleasing and inedible. The products of one’s life demonstrate his internal spiritual condition.