If someone has done you a kindness, you should do him a kindness in return.
A boy was once able to help a circus elephant by stopping another boy from throwing stones as it. A year later the circus elephant was doing his tricks and the ring he caught sight of his benefactor sitting on a hard form. He immediately broke off his performance, lifted the buy up in his trunk and placed him carefully down in a plush-covered seat in the most expensive part of the marquee.
An elephant never forgets, and one good turn deserves another.