So from these narrations above we know that there will be a successor to Imam Mahdi (AS) before his re-appearance. This successor is also known as the Yamani.
(There is no banner better than that of the banner of Yamani, it is the banner of faith and dedication, because he calls to your
possessor (Imam Mahdi, the 12th Imam), so if the Yamani comes out, selling weapons to people or any Muslim becomes
prohibited, and if the Yamani appears, stand up to him, because his banner is the banner of faith, and its prohibited for any
Muslim to turn away from him, and who ever turns away from him, then he's from the people of hell, because he calls to the
truth and to the path that is Mustaqeem(straight)).
Al-Ghaybah - Mohammad Ibn Ibrahim A' Noâmani p. 264.
I wish to tell you that the Yamani (as) and the sign that the greater occultation is almost over has appeared. His name is Ahmad Al-Hassan (as).
He is the Ahmad mentioned by name in the will of Prophet Muhammad (saw).
Abu Abdullah a.s: "This matter shall not be claimed by anyone except by its companion or else Allah shall cut off his age."
Kafi v.1 p.373
In other words the will of the Prophet Muhammad (saw) will not be claimed by anyone except the rightful owner of the will. The will of the
Prophet Muhammad (saw) written on the night of his death, which states that after me there will be 12 Imams and 12 Mahdis, the 1st of the
Mahdis will be Ahmad. He will be the 1st of the close ones (to the 12th Imam (as).
So here we see that the belief that the sunni have about the Mahdi being born at the end of time is not entirely wrong, and is actually correct,
except that the Mahdi born at the end of time is not Imam Muhammad Al-Hassan Al-Mahdi, but is actually his successor Imam Ahmad AlHassan Al-Yamani (as), who is the first Mahdi mentioned in the will of the Prophet Muhammad (saw), he is the messenger of Imam Mahdi (as)
to the Muslims, a messenger from Jesus (as) to the Christians and a messenger from Elijah (as) to the Jews.
O Allah, Hasten, Hasten, Our Master, O the Master of the era, remove this sorrow of his (as) occultation from this nation, make
his (as) arrival smooth, register our names as \