John starts from the very “beginning,” referring to Jesus (1 John 1:3). Jesus is God, and was in the beginning with God (John 1:1). Similar to the opening passages of Genesis and the Gospel of John, 1 John starts with a clear connection between Jesus and God the Father as the beginning of all things. John also refers to the idea of Jesus coming to earth as a flesh-and-blood man (1 John 1:2), which is a critical part of the gospel.
John was closely connected with Jesus. He was a personal witness to Jesus’ earthly ministry. John was one of the closest followers of Jesus. He heard Him teach, saw Him before and after the resurrection, and touched Him with his own hands. John was the last surviving apostle, and so he spoke with an authority few could match. John further calls Jesus the “word of life,” a phrase used elsewhere only in Philippians 2:16.
Chapter 1 re-states the fact that Jesus is the eternal Son of God. John confirms that he has personally seen and heard the things he is teaching. God’s truth is presented as “light,” while false teachings are presented as “darkness.” Those who hold to the truth are saved from sin; those who claim to have no sin at all are self-deceived.
First John 1:1–4 introduces this letter written by the apostle John. John references Jesus’ eternal existence, and His identical nature to God the Father. John also makes a claim to eyewitness testimony: he has personally seen these things he is teaching others about. Mutual fellowship, between Christians, and in Christ, is also mentioned here.