""It should be noted that though many might write concerning Catholic truth, there is this difference that those who wrote the canonical Scripture, the Evangelists and Apostles, and the like, so constantly assert it that they leave no room for doubt. That is what he means when he says 'we know his witness is true.' Galatians 1:9, "If anyone preach a gospel to you other than that which you have received, let him be anathema!" The reason is that only canonical Scripture is a measure of faith. Others however so wrote of the truth that they should not be believed save insofar as they say true things." (St. Thomas Aquinas, Commentary on the Gospel of John 21) [(Romae: Marietti E ditori Ltd., 1952) n. 2656, p. 488.]
In Latin: "Cuius ratio est, quia sola canonica scriptura est regula fidei."
Go figure! Sola Scriptura way before Luther! And in comments made on Galatians 1:9 no less!
Galatians 1:9 As we have already said, so now I say again: If anybody is preaching to you a gospel other than what you accepted, let them be under God's curse!
Excellent