John Chrysostom

But that none should say, An evil tree brings forth indeed evil fruit, but it brings forth also good, and so it becomes hard to discern, as it has a two-fold produce; on this account He adds, A good tree cannot bring forth evil fruit, neither can an evil tree bring forth good fruit.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

"A good tree cannot bring forth evil fruit, neither can a corrupt tree bring forth good fruit." A corrupt tree cannot bring forth good fruit as long as it is diseased. But if it has changed its condition, it can bring forth good fruit. See that He did not say, "it will not be able," but only that as long as it is corrupt it does not bear good fruit.

Commentary on Matthew ↗

Jerome

A good tree cannot bear bad fruit, nor can a bad tree bear good fruit. Let us ask the heretics who claim that there are two contradictory natures, if according to their understanding, a good tree can never bear bad fruit, then how did Moses, a good tree, sin by striking the rock (Deut. 32)? And how did David, after killing Uriah, sleep with Bathsheba (2 Sam. 11)? And how did Peter, during the Passion of the Lord, deny Him, saying: 'I do not know the man' (Matt. 26:72)? …

Commentary on Matthew ↗