Can a fig tree, my Brothers, bear olives? or a vine bear figs? No, nor can a brackish well give good water.
You must assume either that both tree and fruit are good, or that both tree and fruit are worthless; since it is by it's fruits that a tree is known.
And, noticing a solitary fig tree by the road-side, he went up to it, but found nothing on it but leaves. So he said to it: "Never again shall fruit be gathered off you." And suddenly the fruit tree withered up.
Does a spring give both good and bad water from the same source?