The banner of the Mahdi has “Al-Bay’a lilah (Allegiance is to Allah)” written on it - because it is the Banner of Monotheism and the banner of the Household of the Prophet Mohammed (PBUH & His Family). It is black, and it is obligatory to follow it - because it is the prophesied banner of the Yamani who guides towards Imam Mahdi (PBUH & His Family).
Imam Al-Baqir (From Him is Peace) said:
“There is no banner which is more guided than the banner of the Yamani, it is a banner of guidance because he calls towards your companion. If the Yamani emerges then selling weapons becomes impermissible upon the people and every Muslim, and if the Yamani emerges then rise and go to him, for verily his banner is a banner of guidance and it is not permissible for any Muslim to go against him, whoever does so is from the people of hellfire, because he calls to the truth and to the straight path.” - Bihar Al-Anwar, Al-Allamah Al-Majlisi, Vol. 52, p. 232
With this banner Imam Ahmed Al-Hassan (From Him is Peace) clearly demonstrated that it is God who chooses his vicegerent on earth, in a time where most believing communities have pushed the concept of a divinely appointed leader to the back of their minds, or stopped to trust it due to impostors, who falsely clothed themselves with this position.
Since the beginning of his call Imam Ahmed Al-Hassan (From Him is Peace) raised this banner, which reads, “Allegiance is to Allah!” – and it is the only banner on earth which calls exclusively to the ‘Supremacy of Allah’ fulfilling the following hadith…
Abu Abdullah (From Him is Peace) said:
"Verily, we Ahlul-Bayt have a banner, whoever goes ahead of it have renegaded, and whoever is late to it it have perished, and whoever follows it has followed [us], "Allegiance is to Allah" is written in it!"
– 250 Signs until the Appearance of Imam Mahdi, Muhammad Ali Tabatabai, p. 19
Abi Ishaq narrated that Noaf Al-Bukali said: “It is written on the banner of the Mahdi ‘Allegiance is to Allah’.”– Al-Malahim wal Fitan, Al-Sayyid ibn Tawus, Vol. 1, p.141; Kitab Al-Fitan, Naim ibn Hammad, p. 220
Abi Ja’far (From Him is Peace) said:
“When the Riser (PBUH) appears, he appears with the Banner of the Messenger of Allah (PBUH & His Family), the Ring of Solomon (PBUH) and the Stone of Moses (PBUH) and his staff. ” - Bihar Al-Anwar, Al-Allamah Al-Majlisi, Vol. 52, p.351
Narrated to us from Muhammad bin Hasan, narrated to us from Muhammad bin Yahya al-Attar, from Muhammad bin Husain bin Abil Khattab from Safwan bin Yahya from Mandal from Bakkar bin Abi Bakr from Abdullah bin Ijlan that he said:
We were discussing the advent of the Qaim in the company of Abi Abdullah (PBUH) when I asked him: “How would we know about this?” He replied: “When you get up in the morning, a slip of paper will be found below your head with the following written on it: Obedience with recognition.” And it is narrated that the following shall be written on the banner of Imam Mahdi: The Allegiance is for Allah, the Mighty and Sublime.
- Kamaaluddin wa Tamaamun Ni’ma Vol. 2, Chapter 57: Signs of the reappearance of al-Qaim (From him is Peace), Hadith 22
The Messenger of Allah Mohammed (PBUH & His Family) said:
"O Ali, even if what remains from this world is only one day, Allah will lengthen this day until a man from your progeny rules. He will be called The Mahdi (the guided). He guides to Allah and the Arabs will be guided through him, like you guided the disbelievers and polytheists from misguidance" Then he said: " And on the palms of his hands it is written: 'Pledge allegiance to him, for allegiance is to Allah.'" - Mo'jam Ahadeeth Imam Al-Mahdi (AS), Al-Shaikh Ali Al-Korani, Vol.1 p. 167
The Black Banner is the banner of the Messenger of Allah Mohammed (PBUH & His Family) which Gabriel (PBUH) descended with on the day of Badr. The Messenger of Allah Mohammed (PBUH & His Family) raised it on the day of Badr and handed it over after the Battle of Badr to Imam Ali, the Prince of the Believers (From Him is Peace), who in turn raised it on the day of Basra (the Battle of the Camel). This blessed banner was then preserved for the Qaim (From Him is Peace) for the day of his holy and blessed rise.
Abi Baseer narrated that Aba Abdillah (PBUH) said in a long hadith about the Qaim of the Family of Mohammed (PBUH & His Family):
“Then he will shake the banner and will walk by it, so there will remain no one in the East or the West except that they will curse it, and it is the banner of the Messenger of Allah (PBUH & His Family), Gabriel descended with it on the day of Badr.” Then he said: “O Abu Muhammad, by Allah it is not cotton nor silk nor linen.” So I said: “So what is it from?” So he said: “From the paper of paradise, the Messenger of Allah (PBUH & His Family) spread it on the day of Badr, then he wrapped it and pushed it to Ali (PBUH). So it remained with Ali (PBUH) until the day of Basra came, so the Commander of the Believers (PBUH) spread it so Allah opened for him (made him victorious). Then he wrapped it, and it is with us there. No one will spread it until the Qaim rises, so if he rises he will spread it, and no one in the East or the West will remain except that they will curse it.”
– Kitab Al-Ghayba (Book of Occultation), Al-Numani, Vol. 1, p. 318
Abi Baseer narrated that Aba Abdillah (PBUH) said:
“When the Prince of the Believers (PBUH) fought the people of Basra (i.e. in the Battle of the Camel), he spread the banner, the banner of the Messenger of Allah (pbuhahf), so their feet were shaken and by noon they said: “We believe, O son of Abi Talib…” [until he said] “So when it was the day of Siffeen (the Battle of Siffeen) they asked him to spread the banner but he refused. So they beseeched him through Al-Hassan and Al-Hussain (pbut) and Ammar ibn Yasir. So he (meaning Ali pbuh) said to Al-Hassan: “My son, the people have to reach a specific time, and verily this banner will not be spread after me except by the Qaim (pbuh).”
– Kitab Al-Ghayba (Book of Occultation), Al-Numani, Vol. 1, p. 317
The Messenger of Allah Mohammed (PBUH & His Family) said:
“Until Black Banners are raised from the East. They will ask for the Truth/Right but they will not be given it. Then they will ask for it, but they will not be given it. Then they will ask for it, but they will not be given it. So they will fight, and they will be victorious. So whoever realizes him from you, or from your descendants, then let him go to the Imam of my Ahlul-Bayt, even if crawling on ice, for they are Banners of Guidance. They will push it to a man from my Ahlul-Bayt whose name matches mine, and his father’s name matches my father’s name. So he will rule the Earth and fill it with justice and equity as it has been filled with oppression and injustice.” - Mo'jam Ahadeeth Imam Al-Mahdi (AS), Al-Shaikh Ali Al-Koran, Vol. 1, p. 382
Imam Ali (From Him is Peace) said:
"O Amer, if you hear the black banners coming, then break this lock and this box, until you are killed underneath them, so if you couldn't, then roll until you get killed underneath them." - Mo'jam Ahadeeth Imam Al-Mahdi (AS), Al-Shaikh Ali Al-Korani, Vol. 3, p. 79
In the book of Sulaym ibn Qais Al Hilali: Aban narrated that the Prince of the Believers ascended the Minbar and gave a long speech and said:
“Verily me, and the pious of my family and the best of my progeny, are the most gentle when young and the most knowledgeable of adults. We have the banner of truth and guidance, whoever goes ahead of it perishes, and whoever deserts it is destroyed, and whoever holds on to it, has followed [us].”
– Bihar Al-Anwar, Muhammad Baqir Al-Majlisi, 3rd ed., v.34, p.262, hadith 1006
The Prince of the Believers (From Him is Peace) said in a long hadith:
“We have the banner of truth, whoever takes shade in it is protected by it, and whoever races to it, wins, and whoever falls behind it, perishes, and whoever leaves it, falls, and whoever holds on to it, is saved.”
– Bihar Al-Anwar, Muhammad Baqir Al-Majlisi, 3rd ed., v.10, p.111, hadith 1006
It is evident from the above narrations that this banner is a banner of infallibility, that is only raised by its companion. Meaning, it is impossible to be claimed by a liar, otherwise it would be a banner of misguidance and would not be described by the Ahlul-Bayt (From Them is Peace) as a banner of truth and guidance.
In addition, the Ahlul-Bayt (From Them is Peace) commanded us to hold on to it and not to go ahead of it, nor fall behind it. This means that if it is raised, then without a doubt it is the true banner, the banner of Imam Al-Mahdi (PBUH & His Family), and its infallibility is from the infallibility of its companion.
So the texts confirm that the banner of the Qaim (From Him is Peace) is the banner of the Messenger of Allah Mohammed (PBUH & His Family). It was raised only twice before, once by the Prophet Mohammed (PBUH & His Family) and another time by Imam Ali (From Him is Peace). The banner was then preserved for the holy rise of the Qaim (From Him is Peace) who will raise it and fill the earth with justice and equity, just as it has been filled with injustice and tyranny.
As to why these banners were called “The Black Banners of the East”, it is because they will come from the East of the earth.
Thawban narrated that the Messenger of Allah Mohammed (PBUH & His Family) said:
“The black banners come from the East, as if their hearts are pieces of iron, so whoever hears about them, go to them and give allegiance to them, even if crawling on ice!”
– Bihar Al-Anwar, Muhammad Baqir Al-Majlisi, 3rd ed., v.51, p.84, hadith 33
– Ahlul-Bayt Fi Al-Kitab Wal Sunna, Muhammad Al-Rishhary, 2nd ed., p.498, hadith 1200
From Thawban that the Prophet of Allah Mohammed (PBUH & His Family) said:
“Three will fight at your treasure, all of them are the sons of a caliph, then it will not be to anyone of them, then the black banners will rise from the east, and they will fight a fight that no nation has fought before”. Then he mentioned something and said: “If you see him, pledge allegiance to him even if crawling on ice, verily he is the Caliph of Allah the Mahdi”.
– Al-Mostadrak A’ala Al-Saheehayn, Abi Abdillah Muhammad Al-Hakim Al-Naysabory, v.4, p.510, hadith 8432 (Online book: p. 464)
– Kanz Al-Ummal, Al-Muttaqi Al-Hindi, v.14, p.263, hadith 38658.
– Sunan Ibn Maja, Muhammad ibn Yazeed Al-Qozweeny, v.2, p.1367, hadith 4084
Abdullah ibn Mas’ud narrated that the Messenger of Allah Mohammed (PBUH & His Family) said:
“While we were with the Messenger of Allah (PBUH & His Family), some youth from Banu Hashim approached. When the Prophet (pbuhahf) saw them, his eyes filled with tears and his colour changed. I said: ‘We still see something in your face that we do not like (to see).’ He said: ‘We are members of a Household for whom Allah has chosen the Hereafter over the dunya (this world) and verily, my Ahlul-Bayt will face calamity, expulsion and exile after me, until a group of people will come from the East and with them are the black banners. They will ask for the truth/right but will not be given it, so they will fight and will be victorious. Then they are given what they have asked but they do not accept it, until they push it to a man from my Ahlul-Bayt so he fills it with justice and equity just as they filled it with oppression. Whoever lives to see that, let him go to them even if crawling over ice”.
– Sunan Ibn Maja, Muhammad ibn Yazeed Al-Qazweeny, v.2, p.1366, hadith 4082
– Bihar Al-Anwar, Muhammad Baqir Al-Majlisi, 3rd ed., v.51, p.82-83, hadith 27
In conclusion, Aba Al-Sadiq (From Him is Peace) is the Qaim of the Family of Mohammed (PBUH & His Family), who raised the banner, which fulfills the three conditions that the banner of the Qaim (From Him is Peace) mentioned in the hadith of the Ahlul-Bayt (From Them is Peace) is: black, has the words ‘Allegiance is to Allah’ written on it, and it comes from the East.