Either allow the tree to be good, and it's fruit good; or shew the tree to be corrupt, and it's fruit corrupt: for the tree is known by it's fruit.

so every good tree yieldeth good fruit, but a corrupt tree produces bad fruit:

a good tree cannot produce evil fruit, nor can a corrupt tree bear good fruit:

and seeing a fig-tree by the way, He went up to it, and finding nothing upon it but leaves, He saith to it, Let no fruit ever hereafter grow out of thee: and the fig-tree withered immediately.

but I tell you, that from henceforth I shall not drink of the fruit of the vine, until that day when I drink it new with you in the kingdom of my Father.