A.T. Robertson Commentary 1 John 2:9

"He that saith he is in the light and hateth his brother, is in the darkness even until now." — 1 John 2:9 (ASV)

And hateth his brother (κα τον αδελφον αυτου μισων). Sharp contrast between the love just described and hate. The only way to walk in the light (1:7) is to have fellowship with God who is light (1:3,5). So the claim to be in the light is nullified by hating a brother.

Even until now (εως αρτ). Up till this moment. In spite of the increasing light and his own boast he is in the dark.