1 Timothy 4:2

through the hypocrisy of men that speak lies, branded in their own conscience as with a hot iron;

Reference is again made to the passages outlined at the head of this chapter. The very worst mistake that any sincere student of the word of God can make is to assume that teachers of false doctrine are either telling the truth, or that they are unaware of the false doctrines they are teaching. The Scriptures leave no doubt at all on this.

Branded in their conscience as with a hot iron ... This is a description of the "hardened," "blinded," deadened soul in whom the truth principle has utterly perished. It begins by rejecting what is known to be true, but in its progression it leaves the "deluded" totally without moral or spiritual guidelines. The Scriptures contain a great deal of material on the judicial hardening of willful sinners; and those interested in further pursuit of the subject will find a discussion of it in my Commentary on Romans, pp. 392-395.