Easton's Bible Dictionary (1897)
The fourth of the catholic or “general” epistles. It was evidently written by John the evangelist, and probably also at Ephesus, and when the writer was in advanced age. The purpose of the apostle (1:1-4) is to declare the Word of Life to those to whom he writes, in order that they might be united in fellowship with the Father and his Son Jesus Christ.
He shows that the means of union with God are, (1) on the part of Christ, his atoning work (1:7; 2:2; 3:5; 4:10, 14; 5:11, 12) and his advocacy (2:1); and (2), on the part of man, holiness (1:6), obedience (2:3), purity (3:3), faith (3:23; 4:3; 5:5), and love (2:7, 8; 3:14; 4:7; 5:1).