By this, we too are being admonished to keep to the pure and simple doctrine of the gospel, without straying in one direction or another. For it is not enough to have the name and title of Christians, or to bear the mark of baptism: we must continue steadfast in the doctrine of the gospel. As we have said before, our Lord Jesus Christ cannot deny himself. He can only be known in the way he has been revealed to us by God the Father, our own various conceptions of him being irrelevant. The gospel shows us why he came, his office, the benefits that we receive from him and the strength that he gives us. If we do not have the pure and simple doctrine which our Lord Jesus Christ has revealed, we have nothing at all, but if we have been taught it, let us hold on to it to the very end. If we draw back, even just a little, it is nothing short of unfaithfulness. Indeed, we must remember that terrible Fall, where we, together with others, fell and became entangled with so many errors, lies and deceits of Satan, that Jesus Christ was totally unknown to us. Since God has now, in his goodness, taken us from such an abyss, let us resolve to have firm and constant faith, so that we are no longer shaken like reeds in the wind. Let us remain firmly rooted in the gospel, grounded upon the invincible power of our Lord Jesus Christ. In him all the promises of God are ‘yes and amen’ (2 Cor 1:20); their truth and their fulfilment is in him. Therefore, let our faith rest steadfast in these facts. This is what we must retain in our minds from Paul’s teaching in this passage.

John Calvin, Commentary on Galatians 1:6-8