Christ worried about this, and not only worried, but also predicted that it would happen. The world refuses to be changed, even if we preached ourselves to death. Wherever the Gospel arises, therefore, the factions and sects must follow, to spoil it and put it down. The reason is that the devil must sow his seed among the good seed (Matt. 13:25); and wherever God builds a church, he builds his chapel or tabernacle next to it.² Satan always wants to be in the midst of the children of God, as Scripture says (Job 1:6). Christ intends this as a warning to His apostles and loyal preachers. They must maintain a diligent watch against this vice and be careful not to let it intrude itself and cause schisms and dissension, especially in doctrine. It is as if He were to say: “If you want to be My disciples, let your understanding and your ideas in doctrine all be the same. Let no one claim to be the master who knows something new or better, judging or condemning the others. Concentrate on what I command you to preach, not on who is to do the preaching. And preserve harmony among yourselves, so that one does not despise the other or start something new.”  (Luther’s Works, v. 21, pages 212).

…But real trouble and woe arise when this invades spiritual affairs and when the devil plants his seed in Christ’s kingdom, so that it takes root both in doctrine and in life. The result in the area of doctrine is this: Although a man may have the assignment and commission from God to preach the Gospel, others arise, even among his pupils, who claim to know it ten times as well as he does. Thus it is the plague and misfortune of the Gospel to have everyone judging it, becoming a doctor of it on his own, and presuming to be a master in doctrine. This is what happened to Moses, when Korah and his mob rebelled against him and said (Num. 16:3): “Why do you exalt yourselves above the people of God? Are they not all holy? Shall God speak only through Moses and Aaron?” And nowadays they say: “Do we not have as much right to have the Spirit and to understand Scripture as others do?” Right away a different doctrine is served up, and sects are started. Then the judging and the criticizing begin, and particularly the shameful slandering, one party venomously accusing and misrepresenting the other, as we are experiencing right now. This brings on the deadly damage of dividing Christendom and undermining pure doctrine everywhere.  (Luther’s Works, v. 21, pages 211-212).