1 John 2:9

“He that saith he is in the light, &c.] Is in Christ the light, or has the true knowledge of the light of the Gospel, or is illuminated by the Spirit of God; for persons may profess to be enlightened ones, and not be so: wherefore the apostle does not say, he that is in the light, but he that says he is, and hateth his brother; who is so either by creation, as all men are brethren, having one Father, that has made them, and brought them up; or by regeneration, being born of God the Father, and in the same family and household of faith; and so regards such who are in a spiritual relation, whom to hate internally, or not to love, is inconsistent with being in the light, or having faith, which…”

“There is no mean between light and darkness, love and hatred, life and death, God and the world: wherever spiritual life is, however weak, there darkness and death no longer reign, and love supplants hatred; and Luk 9:50 holds good: wherever life is not, there death, darkness, the flesh, the world, and hatred, however glossed over and hidden from man's observation, prevail; and Luk 11:23 holds good. "Where love is not, there hatred is; for the heart cannot remain a void" [BENGEL]. in the light--as his proper element. his brother--his neighbor, and especially those of the Christian brotherhood. The very title "brother" is a reason why love should be exercised. even until now--notwithstanding…”

“He that saith he is in the light - That he has true religion, or is a Christian. See 1 John 1:7. And hateth his brother - The word “brother” seems here to refer to those who professed the same religion. The word is indeed sometimes used in a larger sense, but the reference here appears to be to that which is properly brotherly love among Christians. Compare Lucke, in loc. Is in darkness even until now - That is, he cannot have true religion unless he has love to the brethren. The command to love one another was one of the most solemn and earnest which Christ ever enjoined, John 15:17; he made it the special badge of discipleship, or that by which his followers were to be everywhere known,…”

“He that saith he is in the light - In Christ, united to him. And hateth his brother - The very name shows the love due to him. Is in darkness until now - Void of Christ, and of all true light. 1 John 2:10”

“2:9-11 Another indication of truly knowing Christ is one’s treatment of other Christians. John is again pointing to those who claim to be spiritually enlightened but separate themselves from other Christians with an attitude of superiority. John defines such an attitude as hatred. 2:9 a fellow believer: Literally his brother. The Greek word adelphos (also in 2:11) is a generic term often used to refer to both male and female members of the same family.”

“that saith: Jo1 2:4 he is: Jo1 1:6; Joh 9:41; Rom 2:18-21 and hateth: Jo1 3:13-17 is in: Jo1 2:11; Psa 82:5; Co1 13:1-3; Pe2 1:9 1 John 2:10”