Revelation 1:9

We have now come to that glorious vision which the apostle had of the Lord Jesus Christ, when he came to deliver this revelation to him, where observe, I. The account given of the person who was favoured with this vision. He describes himself, 1. By his present state and condition. He was the brother and companion of these churches in tribulation, and in the kingdom and patience of Christ. He was, at their time, as the rest of true Christians were, a persecuted man, banished, and perhaps imprisoned, for his adherence to Christ. He was their brother, though an apostle; he seems to value himself upon his relation to the church, rather than his authority in it: Judas Iscariot may be an apostle, but not a brother in the family of God. He was their companion: the children of God should choose communion and society with each other. He was their companion in tribulation: the persecuted servants of God did not suffer alone, the same trials are accomplished in others. He was their companion in patience, not only a sharer with them in suffering circumstances, but in suffering graces: if we have the patience of the saints, we should not grudge to meet with their trials. He was their brother and companion in the patience of the kingdom of Christ, a sufferer for Christ's cause, for asserting his kingly power over the church and the world, and for adhering to it against all who would usurp upon it.

— Matthew Henry's Concise Commentary (public domain)

I John--So "I Daniel" (Dan 7:28; Dan 9:2; Dan 10:2). One of the many features of resemblance between the Old Testament and the New Testament apocalyptic seers. No other Scripture writer uses the phrase. also--as well as being an apostle. The oldest manuscripts omit "also." In his Gospel and Epistles he makes no mention of his name, though describing himself as "the disciple whom Jesus loved." Here, with similar humility, though naming himself, he does not mention his apostleship. companion--Greek, "fellow partaker in the tribulation." Tribulation is the necessary precursor of the kingdom," therefore "the" is prefixed. This must be borne with "patient endurance." The oldest manuscripts omit "in the" before "kingdom." All three are inseparable: the tribulation, kingdom and endurance. patience--Translate, "endurance." "Persevering, enduring continuance" (Act 14:22); "the queen of the graces (virtues)" [CHRYSOSTOM]. of, &c.--The oldest manuscripts read "IN Jesus," or "Jesus Christ." It is IN Him that believers have the right to the kingdom, and the spiritual strength to enable them to endure patiently for it. was--Greek, "came to be." in . . . Patmos--now Patmo or Palmosa. See Introduction on this island, and John's exile to it under Domitian, from which he was released under Nerva. Restricted to a small spot on earth, he is permitted to penetrate the wide realms of heaven and its secrets. Thus John drank of Christ's cup, and was baptized with His baptism (Mat 20:22).

— Jamieson-Fausset-Brown Commentary (public domain)