How do we know what is the most precious gem ?

A wise woman who was travelling in the mountains found a precious stone in a stream. 

The next day she met another traveller who was hungry, and the wise woman opened her bag to share her food. The hungry traveller saw the precious stone and asked the woman to give it to him. She did so without hesitation. 

The traveller left, rejoicing in his great fortune. He knew the stone was worth enough to give him security for a lifetime. But a few days later he came back to return the stone to the wise woman.

"I've been thinking," he said, "I know how valuable the stone is, but I give it back in the hope that you can give me something even more precious. Give me what you have within you that enabled you to give me the stone." / Material wants can be driven away not by providing material comforts but by giving spiritual help.