One good turn deserves another.
When someone does you a good deed, you must never forget it. You must look out for the opportunity to do a good deed to that person. If you do not get that opportunity then you must pass on the good deed to someone else. It is quite a strange fact of life, that a good deed done to another always bring some kind of reward to the person who has done the good deed. Hence you must always return good with good.
There is a simple satisfaction in doing good to other. There is a wonderful poem about a man who helps an old woman across the street. The woman blesses him for helping her. At the end of the poem the man expresses the fond hope that some young man like himself will help his mother when she is in trouble.
Therefore, one should never hesitate to do good for others. For one good turn deserves another!