The last of all prophets of God  Muhammad, May Allah bless him and give him peace, made a very significant prophecy when he said that:                                                 

 The above tradition has been quoted in Musnad of Imam Ahmad from Ibn Abbas^RZ, by Abu Nu-aym Isphahani from Ibn Abbas, in Kanzul Ummal from Ali, in Mishkat and it’s commentaries Mirqat and Lumu-at from Imam Jafar and Razeem, by Hakim from Abdullah Ibn Umar ^RZ, and in Tafseer-e-Madarik with some variance in words.                                       

The Tradition Elucidates The Following:

(i) that MAHDI ^pbuh and Jesus ^pbuh are not one and the same person as some  groups tries to make people believe.                

  (ii) that they will not come or live at the same time, one being in the middle and the other at the end of the UMMAH.                                         
(iii) that they would be saviors of UMMAH in the middle and the end of it as the Prophet^pbuh himself was at the beginning.                                
(iv) Imam MAHDI ^pbuh and Jesus ^pbuh would follow the       Prophet^pbuh as saviors. This means that they would be Caliphs of God and hence free from error and that their guidance too would be free from  flaw.                        

  The number of traditions about Imam MAHDI ^pbuh is very large. Perhaps on no other single issue so many traditions could be found. Some of them are sound and some weak. Some traditions do not pertain to Imam MAHDI, but traditionalist's  placed them under the chapters allocated to MAHDI.                                                                                          
A multitude of earlier Muhadatheen (Scholars of Hadith) belonging to Sunnah and Jama-ah believed that from all these traditions, two things are definitely established.                                                                                            

One, the advent of Imam MAHDI^pbuh is a religious must, and secondly, that he would be a descendent of Fatima ^Rz, daughter of the Prophet ^pbuh.  

They believed that these two things are established from continual traditions (Ahadithul-Mutawatirah).

Imam MAHDI – The Caliph of God, not a Monarch.

Now a days, Muslims are disgusted with the state of affairs especially with the widespread corruption, corrosion of faith and un-Islamic practice of those who happen to be at the helm of affairs. They like to believe in myths holding out promises of a sudden change bringing about political domination of Muslims all over the world under a Monarch called MAHDI. They also fail to distinguish a right interpretation in the light of Qur’an and the otherwise. Even in respect of sound traditions people do not appreciate the symbolic nature of predictions. They tend to go with what is apparent and not with the appropriate intrinsic sense in the light of Qur’an.

The Prophet ^pbuh predicted that, after him, there would be a plenty of traditions. He told the followers to accept the traditions that agree with the Book or else, reject them. But the lofty hope of a world-wide Islamic Empire, set up over-night by MAHDI does not let people put such traditions or even their wrong interpretations to the acid test (comparing with Qur’an) given by the Prophet ^pbuh himself.

Thus, some people vehemently expect of their long awaited MAHDI as follows:

(i) that he will be a Monarch of the world

(ii) that under his rein, all men and women living on the earth will eventually become Muslims, leaving no disbeliever, perhaps without putting him to sword.

(iii) That he will fill the whole earth with justice and equity as it would be filled with in-justice and in-equity.

(iv) That he will conquer the city of Qustuntunya.

(v) That he will be a King of Arab, etc.  

Let us examine briefly, the first two notions:

It is accepted by all that Imam MAHDI ^pbuh would be a descendent of Fatima ^RZ. some people saw no harm in buying the concept of a Muslim rule over the entire world converting it to Islam. Consequently, no disbeliever will be left and if at all left, he will perhaps be put to sword. This idea was anchored on the following words appearing in several traditions. 

       The word, Al-Ardh (meaning the earth) can also mean land, country, region, area etc. Nevertheless, people who hold the view that Imam MAHDI ^pbuh will capture unprecedented and unlimited political power, prefer this word to mean only the planet Earth. Grammatically, the preceding “AL” (Alif and Laam) can also make the word to specify a part or some parts of the earth instead of the whole earth. In that case the prophecy would mean that Imam MAHDI^pbuh would spread justice in a part  or some parts of the earth or amongst the people belonging to different parts of the world. The whole earth was never filled with justice. This has never been the way of God.                                 

Holy Qur’an says:

        The first verse above pertains to the Christians and the second to the Jews. These verses indicate that Christians and Jews will exist until the Day of Resurrection and the enmity and hatred among them will also remain until that day. The following verse makes it clear that the notion of all the nations amalgamating to become a single Muslim nation clashes with Qur’an:                                                                              

   Giving guidance is not in the hands of even Caliphs of God. It is within exclusive domain of God.                                                                                  

 Traditions of the Prophet^pbuh also show that this idea is a pure myth:                                                                                                                
(i) Imran Bin Hasan ^Rz related that the Messenger of Allah ^pbuh said that one or the other group of my UMMAH will never cease fighting for the truth until the last of them will fight with Anti-Christ (Dajjal).                                 
                                                      (Abu Dawood, Mishkat) 

(ii) Sauban ^RZ related that the Messenger of Allah ^pbuh said that once the sword will be put (to use) amongst my UMMAH, it will never be withdrawn until the Day of Resurrection.                                                                  
                                            (Abu Dawood, Tirmidhi, Mishkat)

The above traditions show that battles will be fought within the Ummah itself and will continue until the Day of Resurrection. Thus, the idea that all the people becoming a single brotherhood under Islam is contradictory to Qur’an and Ahadith of Prophet ^pbuh.                                                             
Please also note that Jesus Christ ^pbuh too had prophesied about coming of the last of prophets Muhammad ^pbuh as “Ruler of the world”.                                                  
       

What Jesus ^pbuh said was nothing but truth and his prophecy came true with the coming of Muhammad ^pbuh as Mercy of the worlds (Rahmatul-lil-Alameen). However, he did not rule over the world as worldly kings do. True, he was the ruler of the world in the incorporeal sense of the biblical term and not in the corporeal sense. He was ruler of the world because salvation, success and prosperity in life here and the hereafter of the entire mankind depended on believing in him and obeying him with love. This is why Allah declared in the last of His books that:

"ONE WHO OBEYED THE MESSENGER, INDEED HE OBEYED ALLAH."

True, billions of men did not accept him and his “guidance”, yet he ^pbuh remains a ruler and a true ruler of the world. And then remember, neither he^pbuh nor Jesus^pbuh nor MAHDI^pbuh had to be “kings” to guide the people and to spread justice among them. They had to be Caliphs of God and Saviors of the people who accepted and obeyed them. That is why the Prophet ^pbuh urged people to accept and obey Imam MAHDI ^pbuh in the following words.
 

"...THEN WILL COME CALIPH OF GOD, MAHDI. AS YOU HEAR ABOUT HIM, SWEAR FEALTY TO HIM EVEN IF YOU HAD TO CRAWL OVER ICE, SINCE INDEED HE IS THE CALIPH OF GOD."  (IB MAJAH)

Hence, the real promised IMAM MAHDI ^pbuh whose chief identification was the most perfect following of the Prophet ^pbuh, was to be a Caliph of God and not a worldly “king” and that his rule was to be
incorporeal and he had to fill the earth with justice to the extent Allah willed.

MAHDI, the Caliph of God and not the king of Arab:

Some people expect MAHDI ^pbuh to be king of Arab. The idea is based upon a tradition appearing in Tirmidhi as narrated by Abdullah Ibn Umer ^RZ. The Arabic words “ Yamlikul Arab” are translated as “King of Arab”. The Arabic word “Malaka” has a wide range of meaning including to possess, to own, to lay hold, to take over, come into possession or control of, dominate, have power or authority over, hold sway over, over-whelm, to rule, reign etc. Now, to speculate from the words “Yamlikul Arab” that Imam MAHDI ^pbuh will rule over Arab as a king, directly clashes with the notion of his being a monarch of the world.

Secondly, it is neutralized by the very next tradition in the same Tirmidhi Shareef and also narrated by Abdullah Ibn Umer himself. The text of both the traditions is the same, however, the words “Yamlikul Arab” have been replaced, in the second tradition, with the word “Yali”. This Arabic word “Yali” has several meanings such as, to be close, to be in-charge, to be friend, to manage, or to rule etc. The word “Arab” does not appear in the second tradition. This contradiction in the two versions of the same tradition renders the speculation of MAHDI^pbuh being a king of Arab most unlikely.

Thirdly, the word “Yali” can be used for a father or head of the family too. Similarly, the word “Malik” can also be used to denote the head of the family. This is evident from the two traditions noted in the commentaries of Qur’an, Zahidi and Ma-alimut Tanzeel, as given below:

1) It is related from the prophet that he said that one who owns a house, a wife and a servant, he is a “Malik”.

2) Abdullah Ibn Abbas^RZ narrated that one who has a home, wife, children and a servant, and nobody can enter his house without his permission, is one of the Muluk (plural of Malik).

Further, the word “Mahdi” does not appear in both the traditions. However, the scholars of Hadith inferred that these traditions pertain to Imam MAHDI ^pbuh and placed them under the Chapter about “MAHDI”. Even if the traditions pertain to Imam MAHDI^pbuh, it means that he would hold God-given authority as Caliph of God.

Imam MAHDI did not have to Conquer Qustuntunyah:

There are people who believe that MAHDI has to conquer the city of Qustuntunyah to be a true Mahdi. The fact is capturing the city of Qustuntunya is not at all a “sign” of Imam MAHDI^pbuh.

Firstly, because there is no mention of “MAHDI” in the tradition predicting the conquest as related from Abu Hurairah in the Saheeh Muslim, the earliest source.

Secondly, the commander of the army is expressly mentioned by the Prophet ^pbuh to be a descendent of Isaac ^pbuh (Banu Ishaque), whereas Imam MAHDI^pbuh, according to a host of sound traditions, should be a descendent of Ishmael (Banu Isma-eel).Ibn Yousuf Maqdisi, a much later writer, expressed his view that it is suspected that this Ameer may be MAHDI. How this misconception affected the minds of later writers and scholars is evident from an example cited below in “Tanzeehul Fahwa” by the late Allamah Syed Shahabuddin ^RA:
Hadith in Saheeh Muslim: 

The same tradition reported by Abu Nuayeem Ispha-hani is as follows:   

"THEN, JESUS SON OF MARY  WILL DESCEND. THEIR 'AMEER'  "THE MAHDI" WILL SAY, COME, LEAD US IN PRAYERS. HE WILL SAY NO."

 It may be seen that Abu Nuayeem Ispha-hani quoted the Muslim’s Hadith in verbatim but for the word “the MAHDI” suffixed to the word “Ameer”. Imam Muslim (Died 216 Hijri) lived about two hundred years earlier to Imam Abu Nuayeem (Died 430 Hijri).Imam Muslim’s compilation is accepted as most sound and reliable. Unfortunately, all such additions or conjectures no longer remained foreign. Gradually they were assimilated. Hence the belief that Imam MAHDI ^pbuh will be the Ameer of Muslims who will conquer Qustuntunya and will say prayer with Jesus ^{pbuh ,} and help him kill Dajjal etc. etc.

CONCLUSION: 

These and very many other imaginary “signs” and man-made “conditions” have been blocking the way of seeking truth. The most reliable characteristic of the true MAHDI^pbuh is his perfect obedience to Qur’an and following in the foot-steps of the Prophet ^pbuh without a flaw.

During the whole history of Islam, Hazrat Syed Muhammad, son of Syed Abdullah (847 – 910 H) has been the only person who called upon people to verify the truth of his being MAHDI and a Caliph of God by referring his deeds, words and conditions to the Book of Allah (Holy Qur’an) and his perfect following of  Prophet ^pbuh . He (Imam MAHDI^pbuh) said:

  He (Imam MAHDI^pbuh) brought back the object of Deen (Religion) before the eyes of masses. His life and message, even now arouses the spirit of Love of God.

May Allah guide us, Ameen.