John Calvin Commentary 1 Peter 5:12

"By Silvanus, our faithful brother, as I account [him], I have written unto you briefly, exhorting, and testifying that this is the true grace of God. Stand ye fast therein." — 1 Peter 5:12 (ASV)

By Silvanus He exhorts them at the conclusion of the Epistle to constancy in the faith; indeed, he declares that his purpose in writing, was to keep them in obedience to the doctrine they had embraced. But he first commends the brevity of his Epistle, so that reading it would not be tiresome for them; and, secondly, he adds a short commendation of his messenger, so that the living voice might be added to what was written, for this was the purpose of the testimony he gives to his faithfulness.

But the qualification, as I suppose, or think, was added, either as a sign of modesty or to let them know for sure that he spoke according to the conviction of his own mind; and it was unreasonable for them not to agree with the judgment of such a great apostle.

Exhorting and testifying How difficult it is to continue in the faith! Evidence of this is the daily defections of many; nor, indeed, should such a thing be surprising when we consider how great is the fickleness and inconsistency of men, and how great is their inclination to vanity.

But since no doctrine can take firm and permanent root in men’s hearts if it is accompanied by any doubt, he testifies that God’s truth, in which they had been taught, was certain. And, doubtless, unless its certainty is clear to our minds, we will always inevitably waver and be ready to turn at every wind of new doctrine. By the grace of God, he means faith with all its effects and fruits.