A Lion caught a Mouse and was about to eat him. The Mouse begged for his life, promising to repay the kindness one day. Amused, the Lion let him go. Later the Lion was trapped in a hunter's net. The little Mouse heard his roars, ran to him, and gnawed through the ropes until the Lion was free.

Moral: No act of kindness is ever wasted, and even the small can help the great.

From Aesop's Fables, public domain.