2 Peter 1:14

Knowing that shortly I must put off, &c.— Knowing that the laying aside of this my tabernacle approacheth swiftly, in the manner that the Lord Jesus Christ hath made known unto me. Our Lord not only told St. Peter that he was to die a violent death, but also the manner of it: John 21:18. It is inquired, "How did St. Peter know that he was to die shortly?" Now it is generally agreed, that our Lord, in the place above quoted, foretold him that he was to die a violent death; but because there is no express mention of the exact time, some of the ancients say that St. Peter had about this period a vision, declaring to him that the time was now approaching. Others think that our Lord limited the time so far, as that it was to happen before the destruction of Jerusalem; though St. John was to survive that desolation. St. Peter, therefore, hearing, where he now was, of the calamities coming upon the Jewish nation, and learning from those signs and forerunners, that the destruction of that nation was at hand; he from thence concluded, that the time of his own martyrdom must be very speedily. This may be said with certainty,—that the Lord Jesus had told him that he should die a martyr in his old age; and his being now grown old, might help to determine the time of his martyrdom. But I have no doubt that all these evidences were also accompanied with immediate divine intimations. St. Peter wrote by the infallible inspiration of the Holy Spirit of God.