17 A good tree produces good fruit, and a bad tree produces bad fruit. 18 A good tree can't produce bad fruit, and a bad tree can't produce good fruit. 19 So every tree that does not produce good fruit is chopped down and thrown into the fire. 20 Yes, just as you can identify a tree by its fruit, so you can identify people by their actions.
Matthew Henry's Commentary on Matthew 7:17-20
Commentary on Matthew 7:15-20
(Read Matthew 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.