In epistolam D. Pauli Apostoli ad Galatas notae

9 As we have said before, I say also now again, if anyone should preach a Gospel to you besides what you have received, let him be accursed.

Men are accustomed to think that these things are being amplified too much, or spoken in a certain anger. Therefore Paul repeats it generally: If anyone [preaches] another Gospel. He does the same in chapter 5 concerning drunkenness, Of which I have predicted and still predict, etc. The sum of the doctrine is this: That you have your faith resting upon so firm a foundation, namely, the immutable truth of God, by which He promises the remission of sins freely in the Gospel, that it is impossible for any creature to shake it. The cause of certainty is the immutable truth of God, which is so certain that every creature who wishes to call the Gospel into doubt or change it must be accursed.

For first, God Himself, who is above the Angels and all creatures, was the first to bring forth the Gospel in Paradise: The seed of the woman shall crush the head of the serpent.

Therefore the logic is the same. Just as Eve, before the fall, if even an Angel from heaven had said, You will not die, ought to have held him as accursed: so also after the fall, so that we are not deceived again (where God promises that we who believe will not die an eternal death, and that on account of the death of the Son), the whole human race ought to hold as accursed him who dares to call this Gospel into doubt.

He who believes in me shall not taste death forever. Likewise, This is the will of the Father, that everyone who sees the Son and believes in him, may have eternal