John Calvin Commentary Romans 4:19

"And without being weakened in faith he considered his own body now as good as dead (he being about a hundred years old), and the deadness of Sarah`s womb;" — Romans 4:19 (ASV)

In faith, etc. If you prefer to omit one of the negatives, you may interpret it this way: “Being weak in faith, he considered not his own body,” etc.; but this makes no sense. He indeed now shows more fully what might have hindered, and even wholly turned Abraham away from receiving the promise. A seed from Sarah was promised to him at a time when he was not by nature fit for fathering children, nor Sarah for conceiving. Whatever he could see concerning himself was opposed to the accomplishment of the promise. Therefore, so that he might yield to the truth of God, he withdrew his mind from those things that were apparent to him and, so to speak, forgot himself.

However, you should not think that he had no regard whatever for his own body, now dead, since Scripture testifies to the contrary. For he reasoned with himself as follows: “Shall a child be born to a man a hundred years old? And shall Sarah, who is ninety, bear a son?” (Genesis 17:17). But as he laid aside the consideration of all this and resigned his own judgment to the Lord, the Apostle says that he considered not, etc.; and truly, it was a greater effort to withdraw his thoughts from what was plainly before his eyes than if such a thing had merely come into his mind.

And that Abraham’s body had, through age, become incapable of fathering children at the time he received the Lord’s blessing is quite evident from this passage, and also from Genesis 17 and Genesis 18. Therefore, the opinion of Augustine, who says elsewhere that the impediment was in Sarah alone, is by no means to be accepted.

Nor should the absurdity of the objection influence us, which led him (Augustine) to resort to this explanation. For he thought it inconsistent to suppose that Abraham in his hundredth year was incapable of fathering children, as he afterwards had many children. But by this very thing, God made His power more visible, since he who was before like a dry and barren tree was so invigorated by the celestial blessing that he not only fathered Isaac but, as if he were restored to youthful vigor, he afterwards had the strength to father others.

But someone may object and say that it is not outside the course of nature for a man to father children at that age. Although I allow that such a thing is not a prodigy, it is still very little short of a miracle.

And then, consider the many toils, sorrows, wanderings, and distresses with which that holy man had been afflicted all his life; it must be confessed that he was not so much debilitated by age as he was worn out and exhausted by these trials. Lastly, his body is not called barren simply, but comparatively. For it was not probable that he, who was unfit for fathering children in the flower and vigor of his age, should begin to do so only now when his physical nature had declined.

Understand the expression being not weak in faith in this sense—that he did not vacillate or fluctuate, as we usually do under difficult circumstances.

Indeed, there is a twofold weakness of faith. One is that which, by succumbing to trying adversities, causes a falling away from the supporting power of God. The other arises from imperfection but does not extinguish faith itself, for the mind is never so illuminated that many remnants of ignorance do not remain, and the heart is never so strengthened that much doubt does not cling to it.

Therefore, with these vices of the flesh—ignorance and doubt—the faithful have a continual conflict. In this conflict, their faith is often dreadfully shaken and distressed, but eventually it emerges victorious, so that they may be said to be strong even in weakness.