Who is Mahdi-the Savior of Mankind?

Question:
Who is Mahdi-the Savior of Mankind?

Answer:
15th of Sha'ban is the birth anniversary of Imam Mahdi - the Savior of Mankind as promised by the Holy Prophet Muhammad (SAWA)... We have to know more about Imam Mahdi because of two main reasons:
1- It is our Holy Prophet's advice that we know the Imam of our age (as mentioned below)
2- Almost all schools of thought have mentioned a savior but the only religion in which the savior is introduced in detail with authentic sources is Islam. So let's not hesitate in saying yes to the call of our beloved prophet Mohammad (SAWA) and start studying more about our Awaited Imam Mahdi (S.A). The Expected Mahdi (S.A) and Government of Justice in Hadith the Holy Prophet [s] said: "The person who dies and has not known the Imam of his time (Imam Mahdi [S.A] is that of the present time) has died the same as one who died during the Age of Ignorance." Musnad-i-Ahmad-ibn-Hanbal, vol. 2, p. 83; vol. 3, p. 446 & vol. 4, p. 96: Sahih-i-Bukhari, vol. 5, p. 13 & Sahih-i-Muslim vol. 6, p. 21, No.1849.In addition to 25 other references introduced by Sunni scholars. The Holy Prophet [s] said: "Al-Mahdi is of my progeny from the sons of Fatimah [a.s]." Sunan-I-Abu Dawud, vol. 4, p. 107
The Holy Prophet [s] said: "Happiness is for the one who will attend the Qaim of my Ahlul Bayt (Imam Mahdi) and will follow him before his rise. This person will love his (Qaim's) lovers and hate his enemies, and will accept the leadership of the Imams from before his advent. These ones are my friends, and are the most sincere members of my Ummah whom I honour very much."Bihar-ul-Anwar, vol. 52, p. 129
The Holy Prophet [s] said: "Allah will raise a man from my progeny, from my Ahlul Bayt, by whom the earth will be filled with justice thoroughly the same as it has been filled with injustice and oppression."Al-Musannif, vol. 11, p. 371
Imam Amir ul Mu'mineen Ali [a.s] said: "When our Qaim rises, the sky will send down its drops, the earth will grow its plants, enmity will come out from the servants' hearts (in order that they live in peace and brotherly love), and savages and beasts will continue to live together peacefully...."Bihar-ul-Anwar, vol. 52, p. 316
Abil-Jarud said: "I asked Imam Baqir [a.s] whether he knew about my love and sincerity for him and he answered he did. Then, I said I had a question for him to answer me, for my eyes were blind and I scarcely walked, so I could not always go to visit him. He wanted me to express my question. I requested him to inform me of the creed by which he and his household adored Allah, Almighty and Glorious, so that I could worship Him, too, by it. He responded: 'You asked a great thing, though you stated a short expression. By Allah, I give you (your answer of) my religion and the religion of my fathers by which we worship Allah, Almighty and Glorious. It is: the confession of faith that there is no god but Allah, that Muhammad [s] is the Messenger of Allah, with affirmation that what has come to him (the Qur'an) is from Allah, having affection (for us and) for the lovers and obedient to us (AhIul Bayt) and hatred to our enemies, surrender to our cause, awaiting our Qaim (the twelfth Imam, for whom there is a domination that will come whenever Allah wills), and endeavoring (for establishing divine obligatory and lawful matters) and being pious, (with avoiding unlawful things)'."Al-Kafi, vol. 1, p. 34
Imam Baqir [a.s] said: "When our Qaim raises, sets his hand (authority) over the heads of the servants, then, he will give them intellectual development and complete their patience and insights. After that, Allah will extend their sights and their hearing so that there will be no barrier between them and the Qaim when he decides to speak with them, then they hear, and they can watch him while he is in his place."Yaumul Khalas, p. 269
Imam Sadiq [a.s] said: "At the time of Al-Qaim (Al-Mahdi) [a.s] a believer who is in the East can see his (Muslim) brother who is in the West, and vice versa, the one who is in the West can see his (Muslim) brother who is the East."Bihar-ul-Anwar, vol. 52, p. 391Note: Dear reader! Surely the existence of the means of communication such as satellites, televisions and the like can be helpful for us to understand this tradition although none of these technological devices existed when these precious words were uttered. Imam Sadiq [a.s] said: "He (Al-Mahdi) will stay (in a place close to the Kabah) between the Pillar and the Standing place (of Abraham) and will call out saying: "O' group of my administrators and the prominent people of mine whom Allah has stored preparing for my triumph before my advent over the face of the earth! Come to me obediently." Then, his call will reach them while they are in their praying places and at home in their beds whether in the East of the Earth or in its West. So, they hear him with this single call which reaches the ears of every one, and, they totally respond (by coming to him) as well. Then, it takes for them but a moment that all of them gather there, between the Pillar and the Standing-place (of Abraham), attending him [a]."Bihar-ul-Anwar, vol. 53, p. 7
Imam Sadiq [a.s] told his sincere companion, Al-Mufaddal, somethings from the story of Al-Mahdi and his advent, thus: "O' Mufaddal! Tell our followers the data (about Al-Mahdi) in order that they may not doubt in (their) religion. "Bihar-ul-Anwar, vol. 53, p. 6
Imam Mahdi [a.s] said: I am Al-Mahdi and I am the still-living one who will establish justice throughout the world the same as it has been filled with oppression. Surely the earth will never remain without a witness, and people will not live in lack of a leader. Thus, do not retell this deposit except for your (Muslim) brothers who are Men of God. "Kamal-ud-Din, p. 445
Imam Mahdi [a.s] said: "But for the incidents that happen (for Muslims), refer to the narrators of our traditions, (i.e. scholars), because they are my witnesses upon you and I am the witness of Allah upon them."Kamal-ud-Din, p. 484
Imam Al-Mahdi [a.s] wrote in a letter to Ash-Shaykh Al-Mufid: "We are aware of your circumstances and nothing of your affairs is concealed from us."Bihar-ul-Anwar, vol. 53, p. 175
Imam Mahdi [a.s] wrote in a letter to Ash-Shaykh Al-Mufid: "We are not regardless of considering you nor are we forgetful of you, because if it were not so, afflictions would shower upon you and enemies would eradicate you. Hence, fear Allah and obey Him, Glory is to His Majesty."Bihar-ul-Anwar, vol. 53, p. 175
Supplication May Allah (s.w.t.) hastens the reappearance of our 12th Imam [a.s] to establish equality, truth, and justice throughout the world. A Nice Poem about Imam Mahdi by Dana Jomaa.
Imam Mehdi, Ya Imam Mehdi,
When will you arrive?
For without you,
We can't survive.
Imam Mehdi, is the one,
We shall follow,
And those who don't,
We shall swallow.
Where have you been?
For waiting for you,
We have been.
We have missed you,
Missed you dearly too,
When will you arrive?
Nobody knows.
Please come and help us,
You will fulfill your message,
And thus,
Bring peace to the world.
Since you have taught us patience,
Imam Mehdi, we will wait for you,
And we shall never be impatient.
I have a request my Imam,
Please help the oppressed,
And the oppressors,
We shall arrest.
Rush the Imam's reappearance,
Rush the Imam's reappearance,
Allah please rush the Imam's reappearance.
For we need him and need him fast,
This oppression will never last,
Remember the past,
When our beloved Imam Hussein (as),
Was oppressed.
Imam Mehdi, Ya Imam Mehdi

Refrence:

Ref: www.hajij.com