Mahdi ‘Abbasi, the third ‘Abbasid Caliph, had a son by the name of Ibrahim, who was a misguided individual. He showed intense enmity and malice towards Amirul Mo’minin (as) in particular. Once he approached Ma’mun, the seventh ‘Abbasid Caliph, and said to him:
“I saw ‘Ali (as) in my dream. We were travelling together till we reached a bridge whereupon he granted me precedence in crossing it. I said to him: ‘You claim to be the Commander of the Faithful, but we are more deserving of this status’. ‘Ali (as) did not give me a proper answer.”
“How did he answer you?” Mamun questioned.
“He simply greeted me several times by saying ‘Peace, Peace’,” replied Ibrahim.
“By Allah! He has answered you loud and clear,” explained Ma’mun. Ibrahim was puzzled. Ma’mun went on, “He viewed you as an ignorant person, unworthy of responding to. This is because Allah, describing His special servants in the Qur’an, says: “And the servants of the Beneficent Allah are they who walk on the earth in humbleness, and when the ignorant address them, they say: Peace,”4 which is (an expression) indicative of their lack of regard (with respect to the ignorant ones) and their (personal) greatness.
“‘Ali (as) looked upon you as an ignorant person and behaved with you as the Qur’an has recommended when dealing with ignorant persons.”( Hikayat-ha-e-Shanidani, Volume 2, Page 20; Safinatul Bihar, Volume 1, Page 79 )