But when he was in Rome - What was the employment of Onesiphorus is not known. It may have been that he was a merchant, and had occasion to visit Rome on business. At all events, he was at pains to search out the apostle, and his attention was the more valuable because it cost him trouble to find him. It is not everyone, even among professors of religion, who in a great and splendid city would be at the trouble to search out a Christian brother, or even a minister, who was a prisoner, and endeavor to relieve his sorrows. This man, so kind to the great apostle, will be among those to whom the Saviour will say, at the final judgment, "I was in prison, and ye came unto me;" Matthew 25:36.

When he was in Rome - Onesiphorus was no doubt an Asiatic, (probably an Ephesian, see below), who had frequent business at Rome; and when he came sought out the apostle, who, it is supposed, had been confined in some close and private prison, (see the preface), so that it was with great difficulty he could find him out. This man had entertained the apostle when he was at Ephesus, and now he sought him out at Rome. Pure love feels no loads. Here was a true friend, one that sticketh closer than a brother.

But when he was in Rome,.... Upon some business or another, where the apostle was a prisoner:
he sought me out very diligently, and found me; as there might be many prisons in Rome, he went from one to another, till he found him; and was one of those to whom Christ will say hereafter, "I was in prison and ye came unto me", Matthew 25:36 or the reason of his going from place to place in quest of him was this; the apostle was not in any particular place of confinement, but had a lodging where he was kept by a soldier, and which with some difficulty Onesiphorus found out: the manner of his bonds was this; he had a long chain fastened at one end to his right arm, and at the other to the left arm of the soldier that kept him, who constantly attended him in this form, wherever he went; and it is possible that in this way he might have liberty to go about and visit his friends; and this might still make it more difficult for Onesiphorus to find him.

found me--in the crowded metropolis. So in turn "may he find mercy of the Lord in that day" when the whole universe shall be assembled.