Imam Abu Yusuf (May the mercy of Allah be upon him) lost his father as a young child and so his mother sent him to the local launderer to be an apprentice so he could learn the trade and begin earning. On his way, the young Abu Yusuf encountered Imam Abu Hanifa (May the mercy of Allah be upon him) and began sitting in his company.
Abu Yusuf subsequently became Hadrat Imam Abu Hanifa’s student and told him about his mother’s concerns. Imam Abu Hanifa advised him to console his mother by telling her that he had high hopes of a great career from what he was learning instead of being apprenticed to a launderer. The mother was not satisfied by this, and came to Imam Abu Hanifa to complain, saying that she had not sent her son to seek knowledge but to learn a trade so that the family could generate some immediate revenue.
Imam Abu Hanifa tried to reassure the mother and said, “You will see that your son will prosper and eat sweet dishes and delicacies meant only for rulers.” The mother finally acquiesced and left her son in Imam Abu Hanifa’s tutelage. This son would later become an exemplary student and scholar of the Islamic world.
Later in his lifetime, Imam Abu Yusuf served as Chief Justice and the Caliph Harun Rashid (May the mercy of Allah be upon him) would sit in his company. Once the caliph said to Imam Abu Yusuf, “Hadrat, I have had a dish prepared for you and would like it brought to you everyday.” Hadrat Imam Abu Yusuf liked the sweet dish very much and asked what it was. Harun Rashid replied, “This dish is so special that it is prepared for me only seldom but from now on, it will be prepared for you daily because of your exemplary status in knowledge.” Imam Abu Yusuf was grateful but again asked what it was, and the king replied, “This is a sweet dish made from pistachios.” Hadrat Imam Yusuf was at once reminded of the words his great teacher Imam Abu Hanifa had spoken to his mother that her son would be dining on dishes reserved for rulers, for in those times pistachios were considered a rich delicacy.
Taken from http://www.tasawwuf.co