Once, when Prophet Musa was asked who was the most knowledgeable person on earth, he answered, «I am,» without referring the matter back to God. God then revealed there was a righteous servant at the junction of two seas who held knowledge Musa did not. Musa asked to travel with him to learn, and the righteous man — Al-Khidr — agreed, on one condition: Musa must not question anything he did until he explained it himself.

They boarded a ship, and Al-Khidr suddenly made a hole in it. Musa couldn't hold back and asked if he meant to drown its passengers. Al-Khidr reminded him of his promise. Later, they passed a young boy, and Al-Khidr took his life; Musa objected again, unable to stay silent. Al-Khidr reminded him once more, warning that if he asked again, they would have to part ways.

They then came to a stingy village that refused them food, yet found a wall about to collapse, which Al-Khidr repaired without asking for payment. Musa questioned him a third time, and so they parted — but not before Al-Khidr explained the wisdom behind each act: the ship belonged to poor fishermen, damaged so a tyrant king would not seize it; the boy would have brought grief to his believing parents through his future wrongdoing, so God would grant them a better child; and the wall hid a treasure meant for two orphaned children. Musa learned that God's knowledge encompasses everything, and that wisdom often hides behind what looks, at first, like hardship.