There is another interpretation expounded on the verse, One who is gracious to the poor has lent to Hashem, and He will pay him his reward (Mishlei 19:17): If a person does kindness with other people he merits in return that if he himself should later need kindness from others, he will find favor in their eyes and they will help him. But someone who does not do kindness with others, then others will not do kindness with him.
Yet another way one can receive greater reward for his deed than what the deed itself was “worth” is when, for example, a person was about to collapse financially and along came a supporter and assisted him. As a result of that assistance the person succeeded in recovering financially and was then able to support his family and workers. Heaven views the benefactor as though he personally sustained the man, the man’s family and his workers because it was he who brought about all the good. When one thinks about this, he will be encouraged to help others with all his might in any way he can.