Tirmidhi in Vol. 2 of his 'Sahih' (page 270) narrates from Abdullah-ibn-Masoud that the Holy Prophet (S.A.W.A.) said:
'The world shall not cease to exist until a person from my progeny shall conquer the earth. His name is the same as mine'.(85)
In the same place of the afore-mentioned book, he narrates from Abu Huraira that the Holy Prophet (S.A.W.A.) said: 'If there remains not more than a day from the life of the earth ...... a person from my progeny who carries the same name as mine shall appear.(86)
Thereafter he writes: 'This is an acceptable and authentic tradition.'
Ibn-Hajar in his 'Sawae'q' (page 98) narrates from Ahmad, Abu Dawoud and Tirmidhi and all the three from the Holy Prophet (S.A.W.A.) who said:
'The world shall not end until a person from my progeny shall come and rule. His name shall be similar to my name.'
The author of 'Esaaf-ur-Rhagebeen' too has narrated the same.(87)
The author of 'Eqdud-Durar' in the second chapter narrates from 'Sunan' of Imam Abu Bakr Muqarri and he from Abdullah-ibn-Masoud that the Holy Prophet (S.A.W.A.) said:
'The world shall not pass away until a person from my progeny shall conquer it.'
In the same chapter of the afore-said book, he narrates from the book 'Sefat-ul-Mahdi' of Hafez Abu Na'eem and 'Sunan' of Abu Abdullah Muqarri and they two from Abdullah-ibn-Omar who said: The Holy Prophet (S.A.W.A) said:-
'A person from my progeny shall emerge. His name is similar to mine and his morals too is the same as mine. He shall fill the earth with equity and Justice.'
Again, in the same chapter of the afore-said book, he narrates from Hafez Abu Na'eem who in turn narrates from Huzaifa-ibn-Yaman that the Holy Prophet (S.A.W A.) said: 'If there remains not more than a day from the life of the earth, God will make a person to appear from my progeny who carries the same name as mine and whose morals are the same as mine. His agnomen is Abu-Abdullah.(88)
Yet again, in the same chapter of the afore-said book, he narrates from Abdullah-ibn-Omar that the Holy Prophet (S.A.W.A.) said:
'A person from my progeny shall emerge at the end of time. His name and agnomen will be the same as my name and agnomen. He shall fill the earth with Justice just as it had been filled with cruelty and oppression.
What we have written under the afore-mentioned topic is only a few of the noble traditions which mention about the name and agnomen of Hazrat Mahdi.
The author of 'Eqdud-Durar' has specially earmarked a chapter for this matter.
Thus, these and some other traditions together with their lengthy exegesis (which was already mentioned and will be mentioned in future) reveal that his name is Muhammad, his title is Mahdi and his agnomen is Abul-Qasim and this is a well-known matter. However, on the basis of only one or two traditions his name has been mentioned to be Ahmad. Apparently, it has been the independent reasoning of its narrator and a mistake committed from his side. If this reasoning is improper, we may still say that this tradition is insignificant as compared to the other traditions (which are contrary to this one).
The author of 'Tazkerat-ul-Al while mentioning the children of Abu Muhammad Hassan Askari says: Amongst them is Imam Muhammad son of Hassan, son of Ali, son of Muhammad, son of Ali, son of Musa, son of Jafar, son of Muhammad, son of Ali, son of Hussein, son of Ali-ibn-Abi-Talib. His agnomen is Abu-Abdullah and Abul-Qasim and he is the successor, 'Hujjat' (Proof) Master of the age, 'Qa'em' (Upholder) and 'Muntazir' (Awaited one). He shall be the last Imam.
The author of 'Matalib-us-Su'ool', after mentioning the place of birth of Hazrat Mahdi (may the blessing of Allah be upon him and his holy forefathers) says: 'However, his name is Muhammad, his agnomen is Abul-Qasim and his titles are 'Hujjat' (Proof) and 'Khalaf-Saleh' (Virtuous successor). He has also been called as 'Muntazar' (Awaited one).
Ibn-Hajar in his book 'Sawa'eq', after mentioning about Imam Abu Muhammad Hassan Askari writes: 'He did not leave behind any successor but his son Abul-Qasim Muhammad Hujjat whose age at the time of his father's demise was five years. However Allah granted him wisdom at that time and he has been called as 'Qa'em' and 'Muntazar'.
The author of 'Nur-ul-Absar', after mentioning about Mahdi says: 'His name is Muhammad and his agnomen Abul-Qasim. The Imamiyahs have given him such titles as 'Hujjat', 'Mahdi', 'Khalaf-Saleh', 'Qaem' and 'Saheb-uz-Zaman'. The most famous amongst them is Mahdi.(89)
A subtle point: Amongst the strange events (if we do not say that God has dissuaded their hearts) is this that amongst the immediate sons of Imams, none has been bestowed with the title of 'Mahdi' except Qaem Al-e-Muhammad (A.S.). Surely, they were a family which spread for a period of over two hundred and forty years. They owned many children and repeatedly heard this blessed title of 'Mahdi'. Nevertheless amongst their immediate children there was none who was called by the title of 'Mahdi' because, this was something against the custom. It is possible to say that Allah, the Exalted may have dissuaded them from this matter in order to safeguard the position of Mahdi (A.S.).