Several authentic hadiths describe the attributes of Mahdi. Some of these hadiths include the following:
1- Abu Sa’eed al-Khudri said: "The Messenger of Allaah (Peace & Blessings of Allaah be upon Him) said: ‘The Mahdi is of my lineage, with a high forehead and a long, thin, curved nose. He will fill the earth with fairness and justice as it was filled with oppression and injustice, and he will rule for seven years.’" (Sunan Abi Dawud, Kitaab al-Mahdi, 11/375, hadeeth 4265; Mustadrak al-Haakim, 4/557; he said: this is a saheeh hadeeth according to the conditions of Muslim, although al-Bukhaari and Muslim did not report it. See also Saheeh al-Jaami, 6736).
2- Abu Sa’eed al-Khudri reported that the Messenger of Allaah (Peace & Blessings of Allaah be upon Him) said: "At the end of the time of my ummah, the Mahdi will appear. Allaah will grant him rain, the earth will bring forth its fruits, he will give a lot of money, cattle will increase and the ummah will become great. He will rule for seven or eight years. (Mustadrak al-Haakim, 4/557-558; he said: this is a hadith whose isnaad is saheeh, although al-Bukhaari and Muslim did not report it. Al-Dhahabi agreed with him, and al-Albaani said: this is a saheeh sanad, and its men are thiqaat (trustworthy), Silsilat al-ahaadeeth al-saheehah, vol. 2, p. 336, hadeeth 771)
3- Umm Salamah said: "I heard the Messenger of Allaah (Peace & Blessings of Allaah be upon Him) say: ‘The Mahdi is of my lineage and family, from the descendants of Fatimah.’" (Sunan Abu Dawud, 11/373; Sunan Ibn Maajah. 2/1368. Al-Albaani said that it is saheeh in Saheeh al-Jaami, 6734)
4- ‘Abdullaah ibn Mas’ood reported that the Prophet (Peace & Blessings of Allaah be upon Him) said: "The world will not come to an end until the Arabs are ruled by a man from my family whose name will be the same as mine." (Musnad Ahmad, 5/199, hadith 3573. Another version says: "… whose name is the same as mine and whose father’s name is the same as my father’s." Sunan Abi Dawud, 11/370).
5- Jabir (may Allah be pleased with him) said: "The Messenger of Allah (Peace & Blessings of Allah be upon Him) said: ‘‘Isa ibn Maryam will descend, and their leader the Mahdi will say, "Come and lead us in prayer," but he will say, "No, one of them should lead them as an honour to this ummah from Allah."’" The version narrated by Muslim says: "… Then ‘Isa ibn Maryam (Peace be upon him) will descend and their leader will say, ‘Come and lead us in prayer,’ but he will say, ‘No, some of you are leaders over others as an honor from Allah to this ummah.’" (Reported by Muslim, 225).