| Clarke's Commentary on the Bible Thy father which seeth in secret - Let us not be afraid that our hearts can be concealed from God; but let us fear lest he perceive them to be more desirous of the praise of men than they are of that glory which comes from Him. Openly - Εν τω φανερω. These words are omitted by nine MSS. in uncial letters; and by more than one hundred others, by most of the versions, and by several of the primitive fathers. As it is supported by no adequate authority, Bengel, Wetstein, Griesbach, and others, have left it out of the text.
Gill's Exposition of the Entire BibleThat thou appear not unto men to fast,.... Which is just the reverse of the hypocrites, the Scribes and Pharisees; and quite contrary to the customs of the Jews, who when they fasted, particularly on their noted fasts (l), "brought out the ark into the street of the city, and put burnt ashes upon it, and upon the head of the prince, and upon the head of the president of the sanhedrim, and every man upon his own head.'' All which was done, to be seen of men to fast; but Christ directs to such sorts of fasting, and which is to be done in such a manner, as only to be seen by God: but unto thy Father which is in secret; who is invisible, and who sees what is done in secret, and takes notice of the internal exercise of grace; which he approves of, and prefers to outward fastings; and thy Father which seeth in secret, shall reward thee openly: and to have honour from God, is infinitely more than to have the applause of men; for as God delights in, so he will reward his own grace with glory. (l) Misn. Taanith, c. 2. sect. 1.
Geneva Study BibleThat thou appear not unto men to fast, but unto thy Father which is in secret: and thy Father, which seeth in secret, shall reward thee openly.
People's New Testament 6:18 Thy Father... shall reward thee. Our self-denial must be for the eyes of God, not of men.
Jamieson-Fausset-Brown Bible Commentary18. That thou appear not unto men to fast, but unto thy Father which is in secret: and thy Father, which seeth in secret, shall reward thee openly-The "openly" seems evidently a later addition to the text of this verse from Mt 6:4, 7, though of course the idea is implied.
Matthew Henry's Concise Commentary6:16-18 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. | 
