I was in the Spirit on the Lord's day
Not on the Jewish sabbath, which was now abolished, nor was that ever called the Lord's day, and had John meant that, he would have said on the sabbath day; much less the Jewish passover, but the first day of the week is designed; so the Ethiopic version renders it "on the first day"; and is so called just as the ordinance of the supper is called the Lord's supper, being instituted by the Lord, and the Lord's table, ( 1 Corinthians 10:21 ) ( 11:20 ) , and that because it was the day in which our Lord rose from the dead, ( Mark 16:9 ) ; and in which he appeared at different times to his disciples, ( John 20:19 John 20:26 ) , and which the primitive churches set apart for his worship and service, and on which they met together to hear the word, and attend on ordinances, ( Acts 20:7 ) ( 1 Corinthians 16:1 ) ; and Justin Martyr F26 tells us, who lived within about fifty years after this time, that on the day called (th tou) (hliou hmera) , "Sunday", (by the Greeks,) the Christians met together in one place, and read the Scriptures, and prayed together, and administered the ordinance of the supper; and this, he adds, was the first day in which God created the World, and our Saviour Jesus Christ rose from the dead; yea, Barnabas F1, the companion of the Apostle Paul, calls this day the eighth day, in distinction from the seventh day sabbath of the Jews, and which he says is the beginning of another world; and therefore we keep the eighth day, adds he, joyfully, in which Jesus rose from the dead, and being manifested, ascended unto heaven: and this day was known by the ancients by the name of "the Lord's day"; as by Ignatius F2, Irenaeus F3, Tertullian F4, Origen F5, and others; for it must be some day that was known by this name, otherwise it is mentioned to no purpose, because it would not be distinctive from others; for which reason it cannot merely design the day in which John saw this vision, because the Lord appeared on it to him, for this would not distinguish it from any other day. Some have conjectured that this was not the weekly Lord's day observed by the Christians, but the anniversary of Christ's resurrection; and so the Ethiopians still call Easter "Schambatah Crostos", the sabbath of Christ: to understand it of the former is best. Now, though John was driven from the house and worship of God, and could not join with the saints in the public worship of that day; yet he was employed in spiritual contemplations and exercises, and was under a more than ordinary influence of the Spirit of God; and his spirit or soul was wholly intent upon, and taken up with divine and spiritual things, with visions and representations that were made unto his mind, which he perceived in his spirit, and not with the organs of his body; he was in an ecstasy of spirit, and knew not scarcely whether he was in the body or out of it:
and heard behind me a great voice, as of a trumpet;
which was the voice of the Son of God, as appears by what it uttered, ( Revelation 1:11 ) ; and is afterwards said to be as the sound of many waters; and it was behind him, as in ( Isaiah 30:21 ) , it came to him at an unawares, and surprised him, while he was in deep meditation on spiritual things: and it was a very "great" one; it was the voice of a great person, of the Son of God, and expressed great things, and was very sonorous and loud, it was like the sound of a trumpet; and this was partly to awaken the attention of John to it, and partly to express the certainty of the relation he gives of what it said; had it been a low muttering voice, it might be questioned whether John rightly understood it, and whether he might not be mistaken in the account of what he heard; but it being so loud and clear, there is no room for such a doubt.