Brethren - The oldest manuscripts and versions read instead, “Beloved,” appropriate to the subject here, love.
no new commandment - namely, love, the main principle of walking as Christ walked (1Jo 2:6), and that commandment, of which one exemplification is presently given, 1Jo 2:9, 1Jo 2:10, the love of brethren.
ye had from the beginning - from the time that ye first heard the Gospel word preached.