John Calvin Commentary Hebrews 3:14

"for we are become partakers of Christ, if we hold fast the beginning of our confidence firm unto the end:" — Hebrews 3:14 (ASV)

For we are made partakers, etc. He commends them for having begun well; but lest, under the pretext of the grace they had obtained, they should indulge themselves in carnal security, he says that perseverance was needed. For many, having only tasted the Gospel, do not think of any progress, as if they had reached the summit. Thus, they not only stop in the middle of their race, even near the starting posts, but turn another way.

This objection is indeed plausible: "What more can we wish for after having found Christ?" But if He is held by faith, we must persevere in it, so that He may be our perpetual possession. Christ, then, has given Himself to be enjoyed by us on this condition: that by the same faith by which we have been admitted to share in Him, we must preserve so great a blessing until death.

Hence, he says beginning, implying that their faith had only begun. Since hypostasis sometimes means confidence, it can be understood that way here. Yet, I do not object to the term substance, as some have translated it, though I explain it somewhat differently. They think that faith is so called because everything a person may have without it is nothing but vanity. But I regard it this way because we rest on it alone, as there is no other support on which we can rely. The word steadfast or firm also fits this view, for we shall be firmly fixed and beyond the danger of wavering, provided that faith is our foundation. The sum of the whole, then, is that faith, which is only beginning in us, must make constant and steady progress to the end.