True religion is always found in the presence of God. False religion is always practiced with at least one eye on man -- and Jesus teaches us that whether the man is someone else is immaterial.
"Take heed that you do not do your charitable deeds before men, to be seen by them. Otherwise you have no reward from your Father in heaven. Therefore, when you do a charitable deed, do not sound a trumpet before you as the hypocrites do in the synagogues and in the streets, that they may have glory from men. Assuredly, I say to you, they have their reward. But when you do a charitable deed, do not let your left hand know what your right hand is doing, that your charitable deed may be in secret; and your Father who sees in secret will Himself reward you openly" (Matt. 6:1-4).
This entire chapter emphasizes the presence and knowledge of the Father. He is mentioned twelve times here, and the structure of Christ's teaching is built up around this truth. Nothing is outside His gaze; everything must be consciously done in His presence. But everywhere we go, we are also in the presence of men. And the temptation is to remember them, and to forget the Father.
The teaching here assumes that the followers of Christ will be giving alms. The neglect of this duty has encouraged the statism we now live under, just as the current statism discourages a godly concern for the poor. But we are to be Christians, that is, responsive to the Book, and not the current political state. This means that the question concerns when we give alms, not if we give alms. And the fact that we don't call it alms-giving anymore should not slow us down or deter us. We should be helping the poor financially.
Christ also addresses the question of true rewards. It sounds very spiritual to say that "Christianity should be lived out for its own sake." It sounds spiritual but it is very unspiritual. Christ here positively requires his followers to be ambitious for the kind of reward given by the Father. But, He also teaches, this reward is denied to all those who are showboating or grandstanding in front of men.
So it is not whether we shall have a reward; it is which reward we shall have. Seeking a reward from men, and seeking a reward from the Father cannot coexist.
But this includes the tricky question of self-reward. There are many individuals who despise those who seek to draw applause from others -- such behavior is "tacky." People with greater social skills know how to draw attention from a watching world in a subtle manner. And if that is insufficient, then we keep an internal ledger whereby we may applaud ourselves. The point of Christ's teaching is not that you are the only one who knows. His requirement is that the Father keep the books; He should be the only one who knows. As for you, your right hand should not know what your left hand is doing. You do not keep the books.
The Lord teaches us about secret charity and open reward. Returning to the earlier point about rewards, there is nothing wrong with a believer seeking an open reward. The one requirement is that it be left in the hands of the Father. One who is motivated by a selfish ambition cannot leave it there. In the same way, we must practice our deeds of charity in a cryptic, secret manner. How good we are at this should be withheld even from ourselves. This is a godly form of "self-deception." Remember the story Jesus tells about the great day of reckoning (Matt. 25:31-40). Of course, Christ is teaching and requiring humility, not absentmindedness. In short, we should seek to be as secretive as we would like the Father to be open in His reward.