Consequence

Rewards aren't usually linear.  They aren't something to strive for either.  They are more of a consequence.  Good deeds have a consequence.  The reward may or may not come as you comprehend.  If  you help a person or feed someone they may not reciprocate.  That doesn't mean it won't come back to you and yours in some way.

It's a bit silly to think there's a reward.  Humans were made in large part to help each other.  The eye is made to see, but we don't expect a reward when it does.  The legs were made to walk.  We don't expect a reward when they bring us from one place to another.  

Taher, there is a consequence to helping and giving.  You may not be able to understand what it is.