Exposition of the Old and New Testament, by John Gill, [1746-63], at sacred-texts.com
The author of this epistle was John, the son of Zebedee, the disciple whom Jesus loved: he was the youngest of the apostles, and survived them all. He does not indeed put his name to this epistle, as the Apostles Paul, Peter, James, and Jude do to theirs; and it is easy to observe, that when this disciple, in his writings, had any occasion to speak of himself, it was usually by such a circumlocution, as the disciple whom Jesus loved, or the other disciple, studiously concealing his name: so that his not putting his name to this epistle need not create any scruple about his being the author of it, which everywhere breathes the temper and spirit of this great apostle; and whoever compares this epistle, and the Gospel written by him, together, will easily conclude it to be his, both from the style and subject matter of it: besides, as Eusebius asserts (a), this epistle was generally received without scruple, both by ancient and modern writers. It is called "general", because it was not written and sent to any particular church, or person, and not because it was for the general use of the churches, for so are all the particular epistles but because it was written to the Christians in general, or to the believing Jews in general wherever they were; for that it was written to the Jews seems evident from Jo1 2:2. It was called, by some of the ancients, the epistle of John to the Parthians (b); by whom must be meant not the natives of Parthia but the Jews professing to believe in Christ, who dwelt in that empire. We read of Parthian Jews a the feast of Pentecost, Act 2:9, who at that time might be converted, and, upon their return to their own country, lay the foundation of a Gospel church state there Dr. Lightfoot (c) conjectures from a passage in Jo3 1:9 that this epistle was written to the Corinthians; but there does not seem to be any sufficient reason for it. As for the time when, and place where, this epistle was written, it is not easy to say: some think it was written at Patmos, whither the apostle was banished in the reign of Domitian, and where he wrote the book of the Revelations; see Rev 1:9; and here some say he wrote his Gospel, and this epistle, and that a little before the destruction of Jerusalem, and which he calls the last time or hour; and that his design in writing it was to exhort the believing Jews, either in Parthia, or scattered about in other countries, to brotherly love, and to warn them against false Christs and false prophets, which were now gone forth into the world to deceive men; see Jo1 2:18. Others think that it was written by him, when a very old man, after his return from his exile to Ephesus, where he resided during his life, and where he died, and was buried. It is called his "first" epistle general, not that it is the first general epistle, for the other two are written to particular persons, but is the first he wrote, and which is general: the occasion, and manifest design of it, is to promote brotherly love, which he enforces upon the best principles, and with the strongest arguments, taken from the love of God and Christ, from the commandment of Christ, and its being an evidence of regeneration, and the truth and glory of a profession of religion: and also to oppose and stop the growth of licentious principles, and practices, and heretical doctrines. The licentious principles and practices he condemns are these, that believers had no sin in them, or need not be concerned about it, nor about their outward conversation, so be they had but knowledge; and these men boasted of their communion with God, notwithstanding their impieties; and which were the sentiments and practices of the Nicolaitans, Gnostics, and Carpocratians. The heresies he sets himself against, and refutes, are such as regard the doctrine of the Trinity, and the person and office of Christ. There were some who denied a distinction, of persons in the Trinity, and asserted there was but one person; that the Father was not distinct from the Son, nor the Son from the Father; and, by confounding both, tacitly denied there was either, as Simon Magus, and his followers; regard is had to these in Jo1 2:22 and others, as the unbelieving Jews, denied that Jesus was the Messiah, or that Christ was come in the flesh; these are taken notice of in Jo1 2:22. Others, that professed to believe in Jesus Christ, denied his proper deity, and asserted he was a mere man, and did not exist before he took flesh, of the virgin, as Ebion and Cerinthus; these are opposed in Jo1 1:1. And others denied his real humanity, and affirmed that he was a mere phantom; that he only had the appearance of a man, and assumed human nature, and suffered, and died, and rose again in show only, and not in reality; of which sort were the followers of Saturninus and Basilides, and which are confuted in Jo1 1:1. This epistle is, by Clemens Alexandrinus (d), called his "greater" or "larger epistle", it being so in comparison of the other two that follow.
(a) Eccl. Hist. l. 3. c. 24. (b) Augustin. apud Grotium. (c) Hor. Hebr. in 1 Cor. i. 14. (d) Stromat. l. 2. p. 389.