One afternoon Guru Nanak and his company were resting on the banks of the Ganges at Patna. Mardana was idly inspecting a stone he had picked up along the road, thinking of the vast throngs who had come to hear the Guru. "Master," said Mardana, "you teach a way for every person to find liberation. But many of those who listen still seem to spend much of their time in conflict, and in seeking out excitement and other idle pursuits. Why do they waste away their lives so?"
"Most people don't recognize its value," replied the Guru, "although human life is the dearest treasure on this earth."
"Surly everyone can see the value of life," said Mardana.
"No," said Nanak. "Each man places his own value on things according to what he thinks. A different man with different knowledge will place a different value. That stone you found in the dirt will make a good example. Take it to the marketplace and see what you can get for it."
Puzzled, Mardana took the stone to the marketplace and at a stall that sold sweets asked what the vendor would trade for it. The man laughed. "Go away, you're wasting my time."
He next tried a produce seller. "I have paying customers to wait on," said the grocer. "I'll give you an onion for it just to get you out of here."
Mardana tried several more shops with no better response. Finally he came to the shop of Salis Raj, the jeweler. Salis Raj's eyes opened wide when he saw the stone. "I'm sorry," he said, "I don't have enough money to buy your gem. But I will give you a hundred rupees if you will let me look at it a while longer."
Mardana hurried back to the Guru to tell him what had happened.
"See," said Guru Nanak, "how when we are ignorant we mistake a valuable gem for a worthless stone. If someone had told you its value before you knew what it was, you would have thought they were crazy. Such a jewel is human life, and whatever you've traded for it, that is what is yours."