Albert Barnes on Matthew 6:1

Alms. Liberality to the poor and needy. Anything given to them to supply their wants. Our Saviour, here, does not positively command his disciples to aid the poor, but supposes that they would do it of course, and gives them direction how to do it. It is the nature of religion to help those who are really poor and needy; and a real Christian does not wait to be commanded to do it, but only asks the opportunity. See Gal 2:10, Jas 1:27, Lk 19:8.

Before men, etc. Our Lord does not forbid us to give alms before men always, but only forbids our doing it to be seen of them, for the purpose of ostentation, and to seek their praise. To a person who is disposed to do good from a right motive, it matters little whether it be in public or in private. The only thing that renders it even desirable that our good deeds should be seen is, that God may be glorified. See Mt 5:16.

Otherwise. If your only motive for doing it is to be seen of men, God will not reward you. Take heed not to do it to be seen, otherwise God will not reward you.

(1) "?????" or, "righteousness" (2) "of your Father" or, "WITH your Father"