Story of a kind king

Once a king and a Persian slave were sailing in the same boat. The slave had never been at sea, and experienced any calamity. After some time the boat was hit by a storm and started tossing, It as very inconvenient for the passengers. All remained quiet ertept the slave who in fear of being drowned began to cry and tremble, and created inconvenience for the others. The others tried to pacify him by kindness and affection but he didn't hear anybody. When the uneasiness lasted longer the king also became displeased.