But when thou doest alms, let not thy left hand know what thy right hand doeth:

People's New Testament

6:3 Let not thy left hand know what thy right hand doeth. A strong expression to indicate that there must be no publishing of our alms deeds.

Wesley's Notes

6:3 Let not thy left hand know what thy right hand doth - A proverbial expression for doing a thing secretly. Do it as secretly as is consistent, With the doing it at all. With the doing it in the most effectual manner.

Jamieson-Fausset-Brown Bible Commentary

3. But when thou doest alms, let not thy left hand know what thy right hand doeth-So far from making a display of it, dwell not on it even in thine own thoughts, lest it minister to spiritual pride.

Matthew Henry's Concise Commentary

6:1-4 Our Lord next warned against hypocrisy and outward show in religious duties. What we do, must be done from an inward principle, that we may be approved of God, not that we may be praised of men. In these verses we are cautioned against hypocrisy in giving alms. Take heed of it. It is a subtle sin; and vain-glory creeps into what we do, before we are aware. But the duty is not the less necessary and excellent for being abused by hypocrites to serve their pride. The doom Christ passes, at first may seem a promise, but it is their reward; not the reward God promises to those who do good, but the reward hypocrites promise themselves, and a poor reward it is; they did it to be seen of men, and they are seen of men. When we take least notice of our good deeds ourselves, God takes most notice of them. He will reward thee; not as a master who gives his servant what he earns, and no more, but as a Father who gives abundantly to his son that serves him.