Matthew Henry Commentary 1 John 1:1-4

"That which was from the beginning, that which we have heard, that which we have seen with our eyes, that which we beheld, and our hands handled, concerning the Word of life (and the life was manifested, and we have seen, and bear witness, and declare unto you the life, the eternal [life], which was with the Father, and was manifested unto us); that which we have seen and heard declare we unto you also, that ye also may have fellowship with us: yea, and our fellowship is with the Father, and with his Son Jesus Christ: and these things we write, that our joy may be made full." — 1 John 1:1-4 (ASV)

That essential Good, that uncreated Excellence, which had been from the beginning, from eternity, as equal with the Father, and which finally appeared in human nature for the salvation of sinners, was the great subject about which the apostle wrote to his fellow believers. The apostles had seen Him while they witnessed His wisdom and holiness, His miracles, and love and mercy, during some years, until they saw Him crucified for sinners, and afterwards risen from the dead. They touched Him, and so had full proof of His resurrection.

This Divine Person, the Word of life, the Word of God, appeared in human nature so that He might be the Author and Giver of eternal life to mankind, through the redemption of His blood, and the influence of His new-creating Spirit. The apostles declared what they had seen and heard so that believers might share their comforts and everlasting advantages. They had free access to God the Father.

This communion of believers with the Father and the Son is begun and maintained by the influences of the Holy Spirit. The benefits Christ bestows are not like the scanty possessions of the world, causing jealousy in others; but the joy and happiness of communion with God are all-sufficient, so that any number of people may partake of it. And all who can rightly say that their fellowship is truly with the Father will desire to lead others to partake of the same blessedness.