'surely god shall appoint a man from my «ummah» (nation). he continued to the point of saying: he shall fill the earth with justice.'
in the 3rd chapter of the same book, the author narrates from the book of «sefat-ul-Mahdi» written by hafez abu-na'eem who in turn narrates from abu sa'eed khudri and he from the holy prophet (s.a.w.a.) who said:
'Mahdi is from us, the ahl-ul-bait (i.e. people of the house). he is from my «ummah».
the author of «fusul al-muhimma» narrates from abu dawoud and tirmidhi and these two from abdullah-ibn-mas'oud and he from the holy prophet (s.a.w.a.) who said:
'if there remains not more than a day from the life of the earth, god will set the day so long until a person from my «ummah» and progeny who carries the same name as mine appears (and fills the world with justice.)'
the author of «yanabi-ul-muwadda» has narrated (on page 433 of his afore-said book) a tradition from the book «jawaher-ul-aqd'ain» of abu sa'eed khudri. in that tradition the holy prophet (s.a.w.a.) says: 'Mahdi is in my ummah.' also the afore-said author narrates from abu abdullah na'emm-ibn-hemaad (from his book of «al-fatan» and he from hisham-ibn-muhammad and he from the holy prophet (s.a.w.a.) who said:- "Mahdi is from this «ummah» and he is the one who shall lead isa-ibn-maryam.(20)"
ragheb in his «mufradaat» says: «ummah» is any group of people which is formed through things like custom, time or place - making no difference whether that thing brings them together voluntarily or involuntarily and the plural of «ummah» is «-ummam».
one group has said as such:- 'the «ummah» of every prophet are his followers and the one who does not follow his custom will not be included in his «ummah» even though he may have lived during his time. therefore, the «ummah» of islam are those people who follow the islamic rules and all that the holy prophet (s.a.w.a.) has brought making no difference whether he has visited him or not or whether he has lived during his time or not. moreover this applies to all, without any difference in families or tribes even though they may differ from each other from the view-point of language, time and place.
the author is of the opinion that: 'it is apparent that the 'object of making known' i.e. (- 'a' & 'l') in (al-Mahdi) is for covenant; meaning that Mahdi - the one who has been remembered in the heavenly books and about whom the prophets have given glad-tidings to their nations, - shall be from this same blessed «ummah» and not from any other «ummah». so this «ummah» deserves to rejoice and be happy for being honoured such a virtue. it is true that in some of the exceptional and less common traditions we find such contents like this one - «Mahdi is not but isa-ibn-maryam (a.s.)».
ibn-hajar has written (this tradition) in «sawa'eq» on page 89.