John Calvin Commentary Hebrews 10:39

"But we are not of them that shrink back unto perdition; but of them that have faith unto the saving of the soul." — Hebrews 10:39 (ASV)

But we are not of them which draw back, etc. The Apostle made free use of the Greek version, which was most suitable to the doctrine which he was discussing; and he now wisely applies it. He had previously warned them, for fear that by forsaking the Church they might alienate themselves from the faith and the grace of Christ; he now teaches them that they had been called for this purpose, so that they would not draw back. And he again sets faith and drawing back in opposition to each other, and also the preservation of the soul in opposition to its perdition.

Now, let us note that this truth also pertains to us, for we, whom God has favored with the light of the Gospel, should acknowledge that we have been called so that we may advance more and more in our obedience to God, and strive constantly to draw nearer to him. This is the real preservation of the soul, for by doing so we will escape eternal perdition.