A corrupt tree - The word "corrupt" here does not signify, as our translation would seem to indicate, that the tree "had been" good, but had become "vitiated;" but that it was a tree of a useless character, of a nature that produced nothing beneficial.

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.

As is the tree, so is its fruit; if the tree is good, it will bring forth good fruit. The tree that brings forth good fruit, is good antecedent to the fruit it produces; it is first good, and then puts forth good fruit: it is not the fruit that makes the tree good, but makes it appear to be so; but it is the goodness of the tree that makes the fruit good. As a good man does, and will do good works, but his works do not make him a good man; he is so before he performs good works, or he would never be able to do them; these make him appear to be a good man: so a good preacher, that has an experimental knowledge of the doctrines of the Gospel, will deliver out sound doctrine, who is first made so by the gifts and graces of the Spirit of God; and by searching the Scriptures, and examining his doctrines by them, he will be known and appear to be a good minister of Jesus Christ, nourished up in the words of faith and good doctrine; and such a good minister of the Gospel, out of the good treasure of Gospel truths put into his earthen vessel, will bring forth, from time to time, good and excellent truths, to the edification and profit of those that hear: "but a corrupt tree bringeth forth evil fruit"; if the tree is corrupt, the fruit will be corrupt; and as is the preacher, so will be his doctrines: if he is a corrupt preacher, or a man of a corrupt mind, destitute of the truth, his preaching will be such as will tend to corrupt both the principles and practices of men; for such evil men and seducers, out of the evil treasure of false doctrines, which they have received into their judgments, will bring forth, either more secretly or openly, evil tenets in their ministry, which prove of bad consequence to the souls of men.

Even so every good tree bringeth forth good fruit; but a corrupt tree bringeth forth evil fruit.

17. Even so every good tree bringeth forth good fruit: but a corrupt tree bringeth forth evil fruit.

7:15-20 Nothing so much prevents men from entering the strait gate, and becoming true followers of Christ, as the carnal, soothing, flattering doctrines of those who oppose the truth. They may be known by the drift and effects of their doctrines. Some part of their temper and conduct is contrary to the mind of Christ. Those opinions come not from God that lead to sin.