Adam Clarke on 1 John 2:10

He that loveth his brother - That is, his neighbor, his fellow creature, whether Jew or Gentile, so as to bear him continual good will, and to be ready to do him every kind office; abideth in the light - not only gives proof that he has received Christ Jesus the Lord, but that he walks in him, that he retains the grace of his justification, and grows therein.

And there is none occasion of stumbling in him - Και σκανδαλον εν αυτῳ ουκ εστιν· And there is no stumbling block in him; he neither gives nor receives offense: love prevents him from giving any to his neighbor; and love prevents him from receiving any from his neighbor, because it leads him to put the best construction on every thing. Besides, as he walks in the light, he sees the stumbling blocks that are in the way, and avoids them; every part of his path being illuminated. Many fall into sin because they do not see the snares that are in the way; and they do not see the snares because they either have not received, or do not abide in, the light.