When ye fast. — Fasting had risen under the teaching of the Pharisees into a new prominence. Under the Law there had been but the one great fast of the Day of Atonement, on which men were “to afflict their souls” (Leviticus 23:27; Numbers 29:7) and practice had interpreted that phrase as meaning total abstinence from food. Other fasts were occasional, in times of distress or penitence, as in Joel 1:14; Joel 2:15; or as part of a policy affecting to be religious zeal (1 Kings 21:9; 1 Kings 21:12); or as the expression of personal sorrow (1 Samuel 20:34; 2 Samuel 12:16; Ezra 10:6; Nehemiah 1:4; et al.). These were observed with an ostentatious show of affliction which called forth the indignant sarcasm of the prophets (Isaiah 58:5). The “sackcloth” took the place of the usual raiment, “ashes” on the head, of the usual unguents (Nehemiah 9:1; Psalms 35:13). The tradition of the Pharisees starting from the true principle that fasting was one way of attaining self-control, and that as a discipline it was effectual in proportion as it was systematic, fixed on the fasts “twice in the week,” specified in the prayer of the Pharisee (Luke 18:12); and the second and fifth days of the week were fixed, and connected with some vague idea that Moses went up Mount Sinai on the one, and descended on the other. Our Lord, we may note, does not blame the principle, or even the rule, on which the Pharisees acted. He recognises fasting, as He recognises almsgiving and prayer, and is content to warn His disciples against the ostentation that vitiates all three, the secret self-satisfaction under the mask of contrition, the “pride that apes humility.” The very words, “when thou fastest” contain an implied command.
Of a sad countenance. — Strictly, of sullen look, the moroseness of affected austerity rather than of real sorrow.
They disfigure their faces. — The verb is the same as that translated “corrupt” in Matthew 6:19. Here it points to the unwashed face and the untrimmed hair. possibly to the ashes sprinkled on both, that men might know and admire the rigorous asceticism.