Once upon a time, there lived in Basra an old man whose only occupation was caring for and loving his only son who was a handsome young man. The old man invested all his money on his son's education. The young man went away for a few years and acquired an education at a well known university under the great scholars of that age.
The day had arrived for the son to return from his studies and the old man waited at the door for his son. When the son came and met his father, the old man looked into his eyes and felt great disappointment. "What have you learnt my son?" he asked, "I have learnt everything there was to be learnt, father", he said. "But have you learnt what cannot be taught?" asked the father. "Go, my son and learn what cannot be taught", said the old man.

The young man went back to his master and asked him to teach him what cannot be taught.
"Go away to the mountains with these four hundred sheep and come back when they are one thousand", said the master.

The young man went to the mountains and became a shepherd. There for the first time he encountered a silence. He had no one to talk to. The sheep did not understand his language. In his desperation, he would talk to them but they would look back at him as if to say he was stupid. Slowly but surely he began to forget all his worldly knowledge, his ego, his pride and he became quiet like the sheep and great wisdom and humility came to him.

At the end of two years when the number of sheep had grown to one thousand, he returned to his master and fell on his feet. "Now you have learnt what cannot be taught," said the master.

NB. It is interesting to note that the Nabis of Allah Taala (Alayhimus salaam) at some time in their lives, generally before Nubuwwat, tended to sheep, and other such animals.