But when you fast, anoint your head and wash your face,
We are here cautioned against hypocrisy in fasting, as before in almsgiving, and in prayer. I. It is here supposed that religious fasting is a duty required of the disciples of Christ, when God, in his providence, calls to it, and when the case of their own souls upon any account requires it; when the bridegroom is taken away, then shall they fast, Mat 9:15.
Commenting on Matthew 6:16-18
But thou, when thou fastest,.... Christ allows of fasting, but what is of a quite different kind from that of the Jews; which lay not in an outward abstinence from food, and other conveniences of life, and refreshments of nature; but in an abstinence from sin, in acknowledgment and confession of it; and in the exercise of faith and hope in God, as a God...
Verse 17. But thou, when thou fastest, anoint, etc. That is, appear as you do daily. Do not assume any new appearance, or change your visage or dress. The Jews and all neighbouring nations were much in the habit of washing and anointing their bodies.