What Jesus Said
Matthew 7:17 Likewise every good tree bears good fruit, but a bad tree bears bad fruit.
Matthew 7:18 A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit.
Matthew 12:33 "Make a tree good and its fruit will be good, or make a tree bad and its fruit will be bad, for a tree is recognized by its fruit.
Matthew 12:35 The good man brings good things out of the good stored up in him, and the evil man brings evil things out of the evil stored up in him.
Clarke's Commentary on the Bible helps to understand the mystery of Fr. Maciel
“So every good tree - As the thorn can only produce thorns, not grapes; and the thistle, not figs, but prickles; so an unregenerate heart will produce fruits of degeneracy. As we perfectly know that a good tree will not produce bad fruit, and the bad tree will not, cannot produce good fruit, so we know that the profession of godliness, while the life is ungodly, is imposture, hypocrisy, and deceit. A man cannot be a saint and a sinner at the same time. Let us remember, that as the good tree means a good heart, and the good fruit, a holy life, and that every heart is naturally vicious; so there is none but God who can pluck up the vicious tree, create a good heart, plant, cultivate, water, and make it continually fruitful in righteousness and true holiness.”
And from JesusWalk
 "No good tree bears bad fruit, nor does a bad tree bear good fruit.  Each tree is recognized by its own fruit. People do not pick figs from thorn bushes, or grapes from briers.  The good man brings good things out of the good stored up in his heart, and the evil man brings evil things out of the evil stored up in his heart. For out of the overflow of his heart his mouth speaks.