Tertullian

The apostle forbids us to enter into hypothetical questions, or to lend our ears to newfangled statements or to consort with a heretic "after the first and second admonitions." We do not enter into these discussions. Discussion has been inhibited in this way by designating admonition as the purpose of dealing with a heretic. The first reason, too, is because he is not a Christian. The instruction is given in order that he might not, after the manner of a Christian, seem to require correction again and again and "before two or three witnesses." The impression could be created that he ought to be corrected, for the very reason that he is not to be disputed with. The second reason is that a controversy over the Scriptures can, clearly, produce no other effect than to upset either the stomach or the brain.