The following are only some of the traditions about Imam al-Mahdi which Sunnis admit to their authenticity and existence:

The Prophet (S) said: "Even if the entire duration of the world’s existence has already been exhausted and only one day is left (before the day of judgment), Allah will expand that day to such a length of time, as to accommodate the kingdom of a person from my Ahlul-Bayt who will be called by my name. He will fill out the earth with peace and justice as it will have been full of injustice and tyranny (by then)."

Sunni References:

• Sahih al-Tirmidhi, v2, p86, v9, pp 74-75

• Sunan Abu Dawud, v2, p7

• Musnad Ahmad Ibn Hanbal, v1, pp 84,376; V3, p63

The Prophet (S) said: The Mahdi will be of my family, of the descendants of Fatimah (the Prophet’s daughter).

ألمَهديُّ مِن عترتي من ولد فاطمة

Sunni references:

• Sunan Abu Dawud, English version, Ch. 36, Tradition #4271 (narrated by Umm Salama, the wife of the Prophet)

• Sunan Ibn Majah, v2, Tradition #4086

Also:

The Prophet (S) said: "We the children of Abd al-Muttalib are the Masters of the inhabitants of the heaven: Myself, Hamza (ra), ‘Ali (as), Ja’far Ibn Abi Talib (ra), al-Hasan (as), al-Husayn (as), and al-Mahdi (as)."

Sunni references:

• Sunan Ibn Majah, v2, Tradition #4087

• al-Mustadrak, by al-Hakim, on the authority of Anas Ibn Malik

The Messenger of Allah said: "The world will not perish until a man among the Arabs appears whose name matches my name."

Sunni reference: Sahih al-Tirmidhi, v9, p74

In Sahih Muslim, in the Chapter of al-Fitan, there are some interesting traditions on what will happen in the last days of the world. I would like to quote two of them here:

Abu Nadra reported: We were with the company of Jabir Ibn Abdillah... Jabir Ibn Abdillah kept quite for a while and then reported Allah’s Messenger (may peace be upon him) having said: "There would be a Caliph in the last (period) of my Ummah who would freely give handfuls of wealth to the people without counting it.”I said to Abu Nadra and Abu al-Ala: Do you mean Umar Ibn Abd al-Aziz? They said: NO, (he would be Imam Mahdi).

Sunni references:

• Sahih Muslim, English version, v4, chapter MCCV, p1508, Tradition #6961

It is also narrated:

In the end of the time, my Ummah will undergo very hard affliction like never before, so that man can not find any way out. Then Allah will appear a person from my progeny, that is my Ahlul-Bayt, who will fill the earth with justice as it was filled with injustice. The inhabitants of the earth and the inhabitants of the heaven love him. The sky will bring down its water everywhere and the earth will bring all what it can offer and will become green all over.

Sunni references:

• al-Sahih fi al-Hadith, by al-Hakim, as quoted in:

• al-Sawa’iq al-Muhriqah, by Ibn Hajar al-Haythami, Ch. 11, section 1, p250

Also Ahmad Ibn Hanbal recorded:

The Prophet (S) said: "Allah will bring out from concealment al-Mahdi from my Family and just before the Day of Judgment; even if only one day were to remain in the life of the world, and he will spread on this earth justice and equity and will eradicate tyranny and oppression."

Sunni references:

• Musnad Ahmad Ibn Hanbal, v1, p99

It is narrated in Sahih Muslim that:

Jabir Ibn Abdillah al-Ansari (ra) said: I heard the Messenger of Allah saying: "A group of my Ummah will fight for the truth until near the day of judgment when Jesus, the son of Marry, will descend, and the leader of them will ask him to lead the prayer, but Jesus declines, saying: "No, Verily, among you Allah has made leaders for others and He has bestowed his bounty upon them."

Sunni reference:

• Sahih Muslim, Arabic, part 2, p193

Also al-Hafidh Ibn Hajar al-Asqalani mentioned that:

"The Mahdi is of this Ummah, and that Jesus (S) will come down and pray behind him."

Sunni reference: Fat’h al-Bari, by Ibn Hajar al-Asqalani, v5, p362

Prophet Jesus is not the Imam of Muslims, and when he comes back, he will be the follower of the Imam of Muslims who is known as Imam al-Mahdi (as).

In Sahih al-Bukhari, it is narrated that:

The Prophet (S) said: "What would be your situation if the Son of Marry (i.e. Jesus) descends upon you and your Imam is among you?"

Sunni reference:

• Sahih al-Bukhari, Arabic-English, v4, Tradition #658

In conclusion, the belief in the coming Mahdi (as) who is a person other than Jesus (as), is an undeniable fact for all Muslims.