1 John 2:9

He that saith he is in the light and hateth his brother, is in the darkness even until now.

John's style of balancing one statement against another is evident here and throughout the letter. "He that saith" introduces the error he was about to expose. Note also the contrast between light and darkness. Christians are the children of light and walk in the light, but the wicked are children of darkness and walk in darkness.

He ... is in darkness even until now ... It is a mistake to understand John as merely refuting the erroneous teachings of Gnostics. While it may be true enough that Gnostics might have seduced many Christians of that era into receiving a lifestyle of "loveless arrogance,"[26] the great teachings of the apostle were not merely a reaction to such things. He was not merely reacting; he was proclaiming the tremendous truths already revealed by Jesus nearly a whole generation previously. In the sermon on the mount, Jesus said: "If thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great is that darkness" (Matthew 6:23). Thus, the metaphor of light and darkness goes back to Christ himself. Paul likewise received and used the same metaphor, his message in Ephesians 4:17-18 reading thus: "For they live blindfolded in a world of illusion, and are cut off from the life of God through ignorance and insensitiveness."[27] He also wrote, "Cast off the works of darkness" (Romans 13:12), "We are not of the night, nor of darkness" (1 Thessalonians 5:5), "What communion hath light with darkness?" (2 Corinthians 6:14).

He that saith ... "This is the fifth time in this epistle that John pointed out a possible inconsistency between profession and conduct (1 John 1:6,8,10; 1 John 2:4; 1 John 4:20)."[28] If people are troubled today because of the gap between people's profession and their performance, it might help to recall that the problem is indeed an old one.

[26] Ibid.

[27] J. B. Phillips, Letters to Young Churches, a Translation of New Testament Epistles (New York: The Macmillan Company, 1948), p. 106.

[28] Charles C. Ryrie, Wycliffe Bible Commentary, New Testament (Chicago: Moody Press, 1971), p. 1010.