Matthew 6:1
"Take heed that ye do not your alms before men, to be seen of them: otherwise ye have no reward of your Father which is in heaven."
The Pharisees were known for their acts before men. When they prayed, they prayed openly using swelling words to impress everyone with their spirituality. When they gave offerings, they would oftentimes fill their bag with coins and drop it into the temple treasury so everyone could hear the coins falling. The Pharisees were all about the Pharisees. They wanted to be sure that everyone knew how spiritual they were.
On the other hand, God commands us not to do our "alms before men." God wants our purpose for giving not to be recognized by man, but to try and please God. He says that if we give to be seen of men, then our reward has been given which is the recognition of men; however, if we give in secret because it is the right thing to do, then God will openly reward us in this life and in the life to come. Several lessons can be learned from this admonition.
First, every act of giving has its rewards. To say that giving so people can see your acts doesn't have its rewards is not true. God says it is true. Whether you give openly or secretly, there will always be a reward. God's promise of giving and receiving does not stop because someone gives to be seen of men. The giving and receiving principle always works no matter the purpose one gave for giving.
Second, some acts of giving have no reward. This may seem to contradict the previous statement, but it does not. When one gives to be seen of man their reward is that man saw them, but they will never have the reward of the Father rewarding them for they already received their reward.
Third, unseen acts of giving have compound rewards. This is the type of reward every Christian should desire. When someone gives in secret, they get the compound reward of the Father being the giver of the reward and also the Father making sure everyone sees what you have done. Not only will you receive an open reward on Earth, but you will receive your rewards in Heaven as well.
Your purpose determines your reward. No matter what you give, if your purpose is to be seen of man, then you will receive your reward but you will receive no more than being seen of man. If your purpose of giving is to please God, then you will find that the compound reward gives immediate and eternal rewards. You will receive an immediate reward sometime on this Earth, but you will have the privilege of receiving a personal reward from the Father at the Judgment Seat.
Let me ask you, why do you give of your time to serve the LORD? Are you serving the LORD to be seen of man, or are you serving the LORD because it is right? Friend, serving the LORD is always the right thing to do, but there is no purpose of serving Him if you are only doing it to be seen of man. Stop soul winning, running your bus route, teaching a Sunday school class and performing any other ministry just so that you can be seen of man. Serving God for the recognition of man has a very short reward life. If you want rewards that last eternally, then serve the LORD because it's right and He will reward you openly.
Giving tithes, offerings and your service to God always has rewards, but your purpose in doing these things will determine the degree of the reward. Let me encourage you to stop telling everyone what you are doing for God and let God tell everyone for you. He does a better job and it always gives validity to your actions when He does it.