Walk In The Light

In the first four verses of John's first letter, he efficiently contradicted two of the most widespread heresies of his day, Docetism and Cerinthus. In the next three verses, he attacks the core belief of Gnosticism that there is a sharp distinction between the spirit and the flesh, what is done in the flesh has no bearing on the spirit.
John says in 1 John 1:5-7 "This is the message we have heard from Him and announce to you, that God is Light, and in Him there is no darkness at all. If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth; but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin."
In these verses, Light and Darkness are used figuratively to refer to Righteousness and Evil. The statement that God is Light means that God is morally perfect or righteous, being without evil or sin of any kind. John also introduces the idea of having fellowship with God. In verse 4, he spoke of the Christians having fellowship with him as he has fellowship with God; but here he speaks of Christians having intimate fellowship directly with God apart from their relationship with the apostle. The idea of fellowship is intimate relationship; the picture that is used in the New Testament about Christ being the husband and the Church His bride is a wonderful expression of intimate relationship. Literally, Christians are to draw near in intimate relationship with God in a similar way that a bride has intimate relationship with her husband, to understand him deeply and relate to him emotionally, to seek his desires and serve him selflessly.
Obviously, for someone to have this depth of relationship with another person they must live together. A husband and wife cannot understand each other or relate to each other emotionally, seek to fulfill each others desires or serve each other selflessly unless they live together. In the same way, a Christian who does not dwell in the Light where God is cannot develop an intimate relationship with God. They will not be able to understand God, they will not seek to fulfill His will, they will not desire to serve Him selflessly. In short, the Christian who harbors darkness in his or her life cannot know God intimately. Later in this letter John will say, "The one who keeps His commandments abides in Him, and He in him." (3:24). Obedience to God's standard of righteousness, walking in the Light, is the only way to have intimate fellowship with God... and, by the way, assurance of salvation (2 Peter 1:9).