I heard Abu Ja'far (a.s) say: “Umar asked Amirul Mu'mineen (a.s) saying, ‘Tell me about the Mahdi, what is his name?’ He (a.s.) replied: ‘As for his name, my beloved (the Prophet) has bound me not to speak to anyone about it until Allah raises him.‘ He (Umar) then asked, ‘Tell me about his attributes.‘ He (AS) replied, ‘He is a young man of medium height, with a handsome face and beautiful hair, his hair falls on his shoulders, and the light of his face outshines the darkness of his beard and head. By my father, (he is) the son of the best of slave girls.’”