"One of the strongest evidences of true conversion is love to God and man. Those who accept Jesus as their Redeemer have a deep, sincere love for others of like precious faith. Thus it was with the believers at Thessalonica. “As touching brotherly love,” the apostle wrote, “ye need not that I write unto you: for ye yourselves are taught of God to love one another. And indeed ye do it toward all the brethren which are in all Macedonia: but we beseech you, brethren, that ye increase more and more; and that ye study to be quiet, and to do your own business, and to work with your own hands, as we commanded you; that ye may walk honestly toward them that are without, and that ye may have lack of nothing.” AA 262.3"
"If a man say, I love God, and hateth his brother, he is a liar: for he that loveth not his brother whom he hath seen, how can he love God whom he hath not seen?"
Both passages emphasize the importance of brotherly love as evidence of true faith. The EGW passage directly quotes 1 Thessalonians, but the underlying principle aligns strongly with 1 John 4:20.