But ye, brethren. — The last verse was addressed to all those whose consciences would prick them on hearing it read at the Eucharist. Now the writer turns to the orderly brethren, as quite a distinct class. The rhetorical effect of this quick apostrophe would be the same as in the well-known story of Napoleon addressing the rioters, and requesting the gentlemen to separate themselves from the canaille. The distinction is so invidious that every one would hasten to join the ranks of the respectable.
Be not weary in well doing. — This is an exhortation to “the patience of Christ,” for which the Apostle had prayed. The phrase takes for granted that they had been hitherto engaged in “well doing” — i.e., in acting honourably, “walking honestly towards them that are without” (1 Thessalonians 4:12); and St. Paul is anxious to preserve them from “fainting” (as the word is translated in Galatians 6:9), and so slipping into the like idleness and bringing scandal upon the Church.