Whoever loves his brother abides in the light, and in him there is no cause for stumbling.
John says in the third chapter, that we falsely boast of love to God, except we love our brethren; and this is most true. But he now takes love to the brethren as a testimony by which we prove that we love God.
The precept of love is old, yes, but it admits new enforcements and motives suited to each age. In innocence men would love as one blood; in sin and recovery, as partners in hope; in the covenant people, as heirs of the Messiah; and now in the gospel church, with obligations renewed by Christ Himself.
AI summary
Commenting on 1 John 2:7-11
He that loveth his brother,.... As such, and because he is his brother in Christ, and that cordially and sincerely, without hypocrisy and dissimulation, and by love serves him, both in things temporal and spiritual, and so observes the new, and yet old commandment, abideth in the light: it is a plain case, that such a man is in the light of grace, and continues...