If we would hold fast that which is good, we must not tolerate any doctrine that is not the pure doctrine of Christ’s Gospel. There is a hatred that is downright charity: that is the hatred of erroneous doctrine. There is an intolerance which is downright praiseworthy: that is the intolerance of false teaching in the pulpit. Who would ever think of tolerating a little poison given to him day by day? If men come among you who do not preach “all the counsel of God,” who do not preach of Christ, sin, holiness, of ruin, and redemption, and regeneration, – or do not preach of these things in a Scriptural way, you ought to cease to hear them. You ought to carry out the spirit shown by the Apostle Paul, in Gal.1:8:“Though we, or an angel from heaven, preach any other Gospel unto you than that which we have preached, let him be accursed.” - J.C. Ryle
Tract: Hold Fast
What is the best safe-guard against false teaching? Beyond all doubt the regular study of the word of God, with prayer for the teaching of the Holy Spirit. The Bible was given to be a lamp to our feet and a light to our path. (Psalm. 119:105.) The man who reads it aright will never be allowed greatly to err. It is neglect of the Bible which makes so many a prey to the first false teacher whom they hear. They would have us believe that “they are not learned, and do not pretend to have decided opinions.” The plain truth is that they are lazy and idle about reading the Bible, and do not like the trouble of thinking for themselves. Nothing supplies false prophets with followers so much as spiritual sloth under a cloak of humility. - J.C. Ryle
Expository Thoughts on the Gospels: Matthew, [Carlisle, PA: Banner of Truth, 1986], 68, 69.