John Calvin Commentary Hebrews 13:8

"Jesus Christ [is] the same yesterday and to-day, [yea] and for ever." — Hebrews 13:8 (ASV)

Jesus Christ the same, etc. The only way by which we can persevere in the right faith is to hold to the foundation and not depart from it in the smallest degree; for whoever does not hold to Christ knows nothing but mere vanity, even if he comprehends heaven and earth, for in Christ are included all the treasures of heavenly wisdom. This, then, is a remarkable passage, from which we learn that there is no other way of being truly wise than by focusing all our thoughts on Christ alone.

Now, as he is addressing the Jews, he teaches them that Christ had always possessed the same sovereignty which he holds at this day; The same, he says, yesterday, and today, and forever. By these words he intimates that Christ, who was then made known in the world, had reigned from the beginning of the world, and that it is not possible to advance further when we come to him. Yesterday, then, comprehends the entire time of the Old Testament; and so that no one might expect a sudden change after a short time, as the promulgation of the Gospel was then still recent, he declares that Christ had recently been revealed for this very purpose, so that the knowledge of him might continue the same forever.

Therefore, it appears that the Apostle is not speaking of the eternal existence of Christ, but of that knowledge of him which was possessed by the godly in all ages and was the perpetual foundation of the Church. It is indeed certain that Christ existed before he manifested his power; but the question is, what is the Apostle's subject. Then I say he refers to quality, so to speak, and not to essence; for the question is not whether he was from eternity with the Father, but what was the knowledge which people had of him. However, the manifestation of Christ, regarding its external form and appearance, was indeed different under the Law from what it is now; yet there is no reason why the Apostle could not say truly and properly that Christ, as regarded by the faithful, is always the same.