Appearance and Moral Character
There are a number of hadiths in Shiite and Sunni sources about the appearance and the moral character of Imam al-Mahdi (a).

Appearance
According to different hadiths, the Prophet (s) has characterized Imam al-Mahdi (a) as being the most similar person to him. Imam al-Hasan al-'Askari (a) also said that Mahdi's look and moral character are the most similar to the Prophet's (s). According to a hadith from Imam 'Ali (a): "when al-Mahdi (a) begins his uprising, his age will (seem to) be between 30 to 40".Imam al-Hasan al-Mujtaba (a) characterized him as a young person of at most 40 years old with an endless power. Imam al-Sadiq (a) describes him as a perfect middle-aged young man. In response to Abu Salt al-Hirawi's question about the signs of the Reappearance of Imam al-Mahdi (a), Imam al-Rida (a) said: "the sign is that he is very old but he looks young. An observer thinks that he is 40 years old or even younger".

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In the book, Mikyal al-makarim, Imam al-Mahdi (a) is characterized as being handsome, his face shining like the moon. In different hadiths, the details of Imam al-Mahdi's (a) face are mentioned. According to a hadith from the Prophet (s): "Mahdi is from me; he has a broad forehead and a long nose". According to another hadith, the Prophet (a) has characterized Imam al-Mahdi (a) as having an Arabian complexion and an Israelite body, with a mole on his right cheek which shines like a star.Imam al-Baqir (a) has quoted his father and ancestor as saying that Imam 'Ali (a) once said on his minbar: "from my progeny in Akhir al-Zaman, a man will appear whose face is reddish white, whose chest is broad, with strong shoulders and two moles on his back, one with the color of his skin, and the other like that of the Prophet (s)".

Moral and Religious Characteristics
The moral and religious characteristics of Imam al-Mahdi (a) can be examined in two ways:
    Given the hadiths in which he is taken to be the most similar person to the Prophet (s) and given the moral characteristics of the Prophet (s) as described in the Qur'an and the hadiths, the moral and religious characteristics of Imam al-Mahdi (a) can be described accordingly.
    Another way is to consult hadiths which provide independent characterizations of the moral characteristics of Imam al-Mahdi (a). In general, according to Shiite and Sunni hadiths about the moral characteristics of Imam al-Mahdi (a), he is the most modest person towards God and the wisest and the most knowledgeable person.
According to a hadith from Imam al-Husayn (a), "Mahdi can be known with his solemnity and his knowledge of halal and haram, as well as people's needing him and him not needing anyone".

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Imam al-Sadiq (a) has characterized him as an extremely ascetic person whose clothes are rough and his food is oat bread. He is hard on the agents of his government, generous to people, and kind to the poor.Imam al-Rida (a) describes Imam al-Mahdi's (a) character as follows: "he deserves people more than they deserve themselves and is more passionate for people than their parents. He is more modest than other people towards God, and more hard-working in acting upon his own orders, avoiding his own prohibitions more than others". Also, Imam al-Rida (a) has characterized him as the wisest, the most knowledgeable, the most pious, the most patient, the most generous, and the greatest worshipper who talks with angels.