One cold winter a lion was lying asleep in the sun. A mouse came out of its hole and began to jump over the body of the sleeping lion. This woke up the lion.

He caught the small creature and was going to crush it under his heavy paw. The mouse begged pardon and requested the lion to let it go. It also said that it might be of any help to him in future.
The lion simply laughed. He could not imagine that it could be of any help to him. He however, was moved to pity and let it go.
Shortly afterwards, the lion was caught in the net laid by the hunter in the forest. He tried his best to free himself from the net but all his efforts remained fruitless. So he began to lament.
When the mouse heard his lamentation, it came out with its young ones. They sat to work and it did not take them long to nibble at the ropes and cut them with their sharp teeth.
The lion became free and thanked the mouse for its timely help. Now he realized that even a small creature could be of help to the stronger and bigger animals.

Moral:
Kindness never goes unrewarded.