11. joyous . . . grievous--Greek, "matter of joy . . . matter of grief." The objection that chastening is grievous is here anticipated and answered. It only seems so to those being chastened, whose judgments are confused by the present pain. Its ultimate fruit amply compensates for any temporary pam. The real object of the fathers in chastening is not that they find pleasure in the children's pain. Gratified wishes, our Father knows, would often be our real curses.
      fruit of righteousness--righteousness (in practice, springing from faith) is the fruit which chastening, the tree yields (Php 1:11). "Peaceable" (compare Isa 32:17): in contrast to the ordeal of conflict by which it has been won. "Fruit of righteousness to be enjoyed in peace after the conflict" [THOLUCK]. As the olive garland, the emblem of peace as well as victory, was put on the victor's brow in the games.
      exercised thereby--as athletes exercised in training for a contest. Chastisement is the exercise to give experience, and make the spiritual combatant irresistibly victorious (Ro 5:3). "Oh, happy the servant for whose improvement his Lord is earnest, with whom he deigns to be angry, whom He does not deceive by dissembling admonition" (withholding admonition, and so leading the man to think he needs it not)! [TERTULLIAN, Patience, 11]. Observe the "afterwards"; that is the time often when God works.

JFB.