1That which was from the beginning, that which we have heard, that which we have seen with our eyes, that which we saw, and our hands touched, concerning the Word of life 2(and the life was revealed, and we have seen, and testify, and declare to you the life, the eternal life, which was with the Father, and was revealed to us); 3that which we have seen and heard we declare to you, that you also may have fellowship with us. Yes, and our fellowship is with the Father and with his Son, Jesus Christ. 4And we write these things to you, that our joy may be fulfilled.
5This is the message which we have heard from him and announce to you, that God is light, and in him is no darkness at all. 6If we say that we have fellowship with him and walk in the darkness, we lie and don’t tell the truth. 7But if we walk in the light as he is in the light, we have fellowship with one another, and the blood of Jesus Christ his Son, cleanses us from all sin. 8If we say that we have no sin, we deceive ourselves, and the truth is not in us. 9If we confess our sins, he is faithful and righteous to forgive us the sins and to cleanse us from all unrighteousness. 10If we say that we haven’t sinned, we make him a liar, and his word is not in us.
2:5 In contrast to the person lying about knowing God is the obedient one. This person experiences more than just shared fellowship with God. This person experiences the love of God to its fullest. As will be seen later in this epistle, this includes experiencing God’s love and, in turn, expressing it to other believers.
The sense of perfection carries the idea of meeting one’s goal of being everything the person could and should be. It is not flawlessness, but completeness and maturity. When we keep God’s Word, His love achieves its goal in us. It is fully expressed in and through us.
John repeats “by this” in a way parallel to 1 John 2:3. Where in 2:3 assurance of communion is in focus, that communion is now described as an abiding relationship (stated plainly in 2:6). To be “in” God is to be abiding in Him (John 15:4-9). This is the critical part of mutual fellowship introduced in 1 John 1:3.