(1 Corinthians 3:11)

For other foundation can no man lay than that is laid, which is Jesus Christ.

I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel: Which is not another; but there be some that trouble you, and would pervert the gospel of Christ. But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed. As we said before, so say I now again, If any man preach any other gospel unto you than that ye have received, let him be accursed. (Galatians 1:6-9)

Wherefore I give you to understand, that no man speaking by the Spirit of God calleth Jesus accursed: and that no man can say that Jesus is the Lord, but by the Holy Ghost. (1 Corinthians 12:3)

The Epistle of Ignatius to the Ephesians

But the spirit of deceit preaches himself, and speaks his own things, for he seeks to please himself. He glorifies himself, for he is full of arrogance. He is lying, fraudulent, soothing, flattering, treacherous, rhapsodical, trifling, inharmonious, verbose, sordid, and timorous.

Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God. (2 Thessalonians 2:3-4)

But I fear, lest by any means, as the serpent beguiled Eve through his subtilty, so your minds should be corrupted from the simplicity that is in Christ. For if he that cometh preacheth another Jesus, whom we have not preached, or if ye receive another spirit, which ye have not received, or another gospel, which ye have not accepted, ye might well bear with him. (2 Corinthians 11:3-4)