6:4 That thine alms may be in secret. It is not concealment that is required, so much as to avoid ostentation.
Openly. Literally, in the open place, in the last day, when every secret thing is made manifest.
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.