Jesus begins a section of teaching where He compares the righteous to the hypocrites. He starts off by saying do no practice your “righteousness” in public, because if you do you will have no reward from God.
He also says that if you are going to give to someone in need, do so in secret. Don’t let your left hand know what your right hand is doing. If you do this in public, you have already received your reward in full. But if you do so in secret, God will reward you for your righteousness.
Why do so in secret? Why not let everyone know what you’ve been up to? I believe it comes down to a simple thought…who are you doing it for? If you’re only giving so that you can be seen and thought well of by others…who are you loving, your neighbor or yourself? Doing so in secret confirms that you are thinking about the individual and not yourself. God wants us to love others…that’s hard to do when we are only focused on self. It’s not that God doesn’t want you to be rewarded…He just wants you giving because of the person, not because of self.
A Journey With Jesus 