The idea proposed by certain people that the hadith regarding the coming of Hazrat Mahdi (as) are weak is definitely incorrect and is corruption in Islam. Some people opposed to the idea of the system of the Mahdi (as) say, “The hadith regarding the system of the Mahdi (as) appear in part in Bukhari and Muslim, and partly in Ibn Majah, the Sunan Nasai, the Sunan Abu Dawud and Tirmidhi,” thus imagining, in their own eyes, they can weaken these and quietly do away with them. According to their own low intellects, they are trying to imply that these hadith are of no value. But this is a most dishonest and false way of behaving.
The hadith regarding the return of the Prophet Jesus (as) are reliable and completely trustworthy.
Sahih Bukhari and Muslim reveal that Muslims will have an imam (religious leader), in other words Hazrat Mahdi (as), at their head when the Prophet Jesus (as) returns in the End Times. It is clearly stated that the Prophet Jesus (as) will return and that the moral values of Islam will rule the world. Even if there were no reference to Hazrat Mahdi (as) in the hadith there are still trustworthy hadith and three verses of the Qur’an that make it clear that the Prophet Jesus (as) will be instrumental in Islam ruling the world. But there is a very important matter here. If the events connected with Hazrat Mahdi (as) revealed in the hadith have taken place (and hundreds of signs described by our Prophet (saas) have taken place one after the other since Hijri 1400), then there can be no question as to whether those hadith are trustworthy or not. The hadith that have come about must be completely reliable, and since they have come about they become stronger than generally agreed hadith.
Hadith about the Prophet Jesus (as) and Hazrat Mahdi (as)
Abu Huraira. He said: What will you do when Jesus, son of Maryam, descends among you and when your imam in the prayer is Hazrat Mahdi (as) (and Jesus follows your imam)? (Interpretation of Sahih Bukhari Mukhtasari Tajri al-Sarih, Hadith No: 1406, Publications of Department of Religious Affairs, Ankara 1986, v. 9, p. 182)
... ...Finally Hazrat Mahdi (as), the spiritual leader of Muslims, will say to Jesus (as), Son of Maryam: “Come and lead us in prayer (salat).” At this, Jesus (as) will say, “No. As a blessing on this community from Allah some of you are the commanders of others.” (He will bestow the position of imam on Hazrat Mahdi [as]). (Sahih Muslim, Vol. 1, p. 209)
Abdullah ibn Masud. Rasulullah (saas) said: “The world will not come to an end until a man from my Ahl al-Bayt [Hazrat Mahdi (as)] whose name is compatible with mine imposes his rule over all the Arabs.” (Abu Dawud, Mahdi, 7)
“If just one day of the life of this world remains, Almighty Allah will prolong it and someone from my Ahl al-Bayt will come.” (Abu Dawud, Mahdi, 7)
I swear to the One in Whose possession my life lies that, the son of Mary (Jesus) will soon descend among you as a just judge. He will break the cross (abolish worshipping the cross), slay the pig (declare the unlawfulness of eating pork) and lift the jizya [capitation tax]: goods will be so plentiful that none will accept any more. (Sunan Tirmidhi, 4/93)
Abu Huraira narrated, "The Prophet (saas) said: 'There is no prophet between me and him, that is, Jesus, peace be upon him. He will definitely descend (to the earth). When you see him, recognize him: a man of medium height, reddish hair, wearing two light yellow garments, looking as if water drops were falling down from his head though it will not be wet. He will fight the people for the cause of Islam, render the dajjal (antichrist) ineffective. Then he will live on the earth for forty years and then he will die. The Muslims will pray over him.'" (Bukhari, Muslim, Abu Dawud and Tirmidhi, Great Collection of Hadith, Rudani, v. 5, p. 380)
I swear to Allah Who holds my breath in His hand that Jesus, son of Maryam will descend among you as a just judge. He will break the cross and slay the pig, and he will abolish the tax on non-Muslims. Goods will be so plentiful that nobody will want any more. (Sahih Muslim, 6/532)
The Last Day will not take place until Jesus son of Maryam (as) descends as a just judge and imam (head of state). (When he descends) he will break the cross (abolish worshipping the cross), slay the pig (declare the unlawfulness of eating pork) and lift the jizya [capitation tax]. There will be so many goods that nobody will accept any more. (Sunan Ibn Majah, 10/340)
... Hazrat Mahdi (as) is from the line of my daughter Fatima. (Sunan Abu Dawud, Vol. No. 14, Page No. 402, 4284)
If there were only one day left for the world, Allah will send a person, Hazrat Mahdi (as), from my Ahl-al Bayt; just as the earth is filled with cruelty, He will fill THE EARTH with justice. (Sunan Abu Dawud, Volume No. 14, Page No. 402, 4283)