The KJV translates the final verb ‘reward thee openly’ and the NKJ follows suit. This reading is found in the Received Text and the Majority Text.
Take steps, says Christ, to ensure that the only reward you are in a position to receive is the reward that God will give. Cut off all possibility of receiving any other reward and by doing so place yourself beyond the reach of temptation. The meaning of the saying, ’and do not let your left hand know what your right hand is doing’ is explained here: it is a figure for acting in secret. What a difference it makes to the way we do our acts of mercy if we do not expect to receive a reward from men. We stop focusing on ourselves and how we appear in the eyes of men; we are set free from the tyranny of nurturing self-image; and we are enabled to do genuine good to others with self out of the picture. We are content that God sees and our faith in his constant supervision of all the affairs of our lives increases. We live a secret life with the Lord in our hearts. As we know he sees when we do good, so we know he sees when we do evil and our resistance to sin is strengthened; we live in the presence of God and we have fellowship with him. That secrecy becomes a precious thing to us for it is the token of God’s presence with us. How terrible is the bondage of being able to do nothing unless we are watched by some other human being! We have ceased to be individuals in our own right and have become extensions of other people’s approval; we have become dependent on those whose praise we seek. Yet though men may praise us, do they really care for us. It is all illusion. The praise seeker imagines that he has real value in the eyes of those who admire him, but human praise is fickle and he is a fool who trusts in it. They may turn just as easily to another object of fascination when the wind changes.
This teaching of Christ has application in the way we organize church giving. Stewardship should be done in a secret way. The offering will be collected more discreetly via a bag, than via an open plate. If the church takes advantage of tax savings in its giving, it will give the administration of this to one person, so that as few as possible know what other members of the church are giving. We believe in common purse; you give to the general offering and no one knows. Some want to give princely sums, and they want it to be known. Perhaps they even want to create a fund in their name, or have a plaque attach to the item they have donated. No, give anonymously to a common purse.
How then does a public figure obey these words? It is of course necessary that a public person should do his work in public and only a novice would understand Christ to forbid this. He cannot simply hide himself from the public eye; he has somehow to obey the Lord even though he continues to operate openly. Even then, there will be other parts of his life in which he can obey this command literally. He will have acts of private charity which must not be paraded. But when he is obliged to act in public, he must still study to not let his left hand know what his right hand is doing; he must turn his thoughts away from his own accomplishments and not meditate on his own glory. He must remind himself that his office and his service to God or man is not something that he deserves; that any gifts he has been given, have been given by God. Though others may be more worthy of the privilege, he has been chosen for the task and he must carry it out to the best of his ability, but carry it out for the good of those he serves. Certainly it is a dangerous thing for a novice to be too quickly elevated to a position of leadership, for Paul warns that this is likely to go to his head, and he may fall into the condemnation of the devil, who was puffed up with pride. This danger should recede in time – assuming that people practice mortification of the flesh – for they learn better to mistrust their natural judgment and to become suspicious of their own motives; they learn more about the traps and snares that Satan has ready for the unwary believer. They have tasted already the vanity of pride and no longer seek after it with the same youthful vigour. Humility, which is the work of God’s Spirit in us over time, has become the rule of their lives. Not that any believer can afford to relax his vigil against sin; he must keep that up to his dying day.
Some teach that if you give to God, you get twice as much back. We dismiss that entirely. There is nothing here about getting back in kind, money for money, nothing about getting back double what you give, nothing about when you receive a reward from God. Maybe it will be in eternity, or maybe you give to the cause of Christ and you do have a great need later and God will sustain you, but probably not by making you wealthy. He may give you assurance, or he may give you instrumentality: you do not know.