Augustine of Hippo, on Matt 12:33

“Either make the tree good and its fruit good: or make the tree evil, and its fruit evil. For by the fruit the tree is known.”

“(Serm. 72. 1.) Or this is an admonition to ourselves that we should be good trees that we may be able to bring forth good fruit; Make the tree good, and its fruit good, is a precept of health to which obedience is necessary. But what He says, Make the tree corrupt, and its fruit corrupt, is not a command to do, but a warning to take heed, spoken against those who being evil thought that they could speak good things, or have good works; this the Lord declares is impossible. The man must be changed first, that his works may be changed; for if the man remains in that wherein he is evil, he cannot have good works; if he remains in that wherein he is good, he cannot have evil works. Christ found us all corrupt trees, but gave power to become sons of God to them that believe on His name.”

Imported from an open dataset — not yet checked against the printed edition.