Jamieson, Fausset and Brown on 1 Thessalonians 5:14

14. brethren--This exhortation to "warm (Greek, 'admonish,' as in 1Th 5:12) the unruly (those 'disorderly' persons, 2Th 3:6, 11, who would not work, and yet expected to be maintained, literally, said of soldiers who will not remain in their ranks, compare 1Th 4:11; also those insubordinate as to Church discipline, in relation to those 'over' the Church, 1Th 5:12), comfort the feeble-minded (the faint-hearted, who are ready to sink 'without hope' in afflictions, 1Th 4:13, and temptations)," applies to all clergy and laity alike, though primarily the duty of the clergy (who are meant in 1Th 5:12)."

support--literally, "lay fast hold on so as to support."

the weak--spiritually. Paul practiced what he preached (1Co 9:22).

be patient toward all men--There is no believer who needs not the exercise of patience "toward" him; there is none to whom a believer ought not to show it; many show it more to strangers than to their own families, more to the great than to the humble; but we ought to show it "toward all men" [Bengel]. Compare "the long-suffering of our Lord" (2Co 10:1; 2Pe 3:15).