Calvin's Commentaries, Vol. 31: Matthew, Mark and Luke, Part I, tr. by John King, [1847-50], at sacred-texts.com
16. Moreover, when you shall fast, be not, like the hypocrites, dejected: 447 for they disfigure their faces, that it may be evident to men that they fast. Verily I say to you, they have their reward. 17. But thou, when thou fastest, anoint thy head, and wash thy face, 18. That it may not appear to men that thou fastest, but to thy Father, who is in secret, and thy Father, who seeth in secret, will reward thee openly.
He again returns to the former doctrine: for, having begun to rebuke vain ostentation in alms and prayer, he laid down, before proceeding farther, the rule for praying in a right manner. The same injunction is now given to his disciples about fasting, which he had formerly given about prayers and alms, not to be too solicitous to obtain the applause of spectators, but to have God as the witness of their actions. When he bids them anoint their head, and wash their face, his language is hyperbolical: 448 for Christ does not withdraw us from one kind of hypocrisy, to lead us into another. 449 He does not enjoin us to counterfeit splendor, or exhort us to temperance in food in such a manner, as to encourage the luxuries of ointments and of dress: but merely exhorts us to preserve moderation, without any thing new or affected;—in short, that the fastings, in which we engage, should make no change in our accustomed way of living.
Thy Father will reward thee When he promises a reward from God to fastings, this mode of expression, as we said a little before with respect to prayer, is not strictly accurate. There is a wide difference, indeed, between prayer and fastings Prayer holds the first rank among the antics of piety: but fasting is a doubtful operation, and does not, like alms, belong to the class of those actions which God requires and approves. It is pleasing to God, only so far as it is directed to another object: and that is, to train us to abstinence, to subdue the lust of the flesh, to excite us to earnestness in prayer, and to testify our repentance, when we are affected by the view of the tribunal of God. The meaning of Christ’s words is: “God will one day show that he was pleased with those good works, which appeared to be lost, because they were concealed from the eyes of men.”
“D'un regard triste, ou, visage chagrin;” — “of a sad look, or, distressed countenance ”
“C'est une facon de parler hyperbolique, c'est a dire, excessive.” — “It is a hyperbolical, that is, an exaggerated way of speaking.”
“Pour nous faire retomber en 1’autre;” — “to make us fall into the other.”