6:16-18 Religious fasting is a duty required of the disciples of Christ, but it is not so much a duty itself, as a means to dispose us for other duties. Fasting is the humbling of the soul, Ps 35:13; that is the inside of the duty; let that, therefore, be thy principal care, and as to the outside of it, covet not to let it be seen. God sees in secret, and will reward openly.

17. But thou, when thou fastest, anoint thine head, and wash thy face—as the Jews did, except when mourning (Da 10:3); so that the meaning is, "Appear as usual"—appear so as to attract no notice.