I said to him, ‘O son of the messenger of Allah, who is the Imam and successor after you?’ He got up hastily and went in the house. Then, he came out holding a three-year-old boy, whose face was like a full moon, on his shoulder and said, ‘O Ahmad, were it not for your honor near Allah the Almighty and near His authorities, I would not show you this, my son. He was named and surnamed like the messenger of Allah (a). He will fill the earth with justice and fairness after it has been filled with injustice and oppression. O Ahmad, he, in this nation, is like al-Khidhr (Elijah) and Thul Qarnayn. By Allah, he will hide in an occultation, during which no one shall be saved except one whom Allah fixes on the believing in his Imamate and supplicating Allah to hasten his deliverance.’ I said, ‘Is there any sign so that I may be sure?’ The young boy said, ‘I am the representative of Allah in His earth and the avenger on His enemies. Do not look for a sign after a proof!’
I left delightedly. On the following day, I came back to him and said, ‘O son of the messenger of Allah, my delight was so great for what you favored me with. Would you please tell me what norm with al-Khidr and Thul Qarnayn was?’
He said, ‘Long occultation.’
I said, ‘O son of the messenger of Allah, shall his (Imam al-Mahdi’s) occultation last long?’
Imam Hasan Al-Askari (a) said, ‘Yes, by my Lord, until many of those, who believe in this matter (occultation and reappearance), shall apostatize, and no one shall remain (believing) except those whom Allah has taken from them a covenant on our guardianship, fixed faith in their hearts, and supported them with a mercy from Him. O Ahmad, this is a command from Allah, a secret from the secrets of Allah, and an unseen matter from the unseen of Allah. Take what I told you, and be from the grateful, you shall be with us in Illiyin.”
2. Muhammad bin Uthman al-Umari narrated that his father said, “Once, I was with Abu Muhammad al-Hasan bin Ali (al-Askari) when he was asked about the tradition transmitted from his father that the earth would not be empty from an authority from Allah over His people until the Day of Resurrection, and that whoever died without knowing the Imam of his age would die as an unbeliever. He said, ‘This is true as day is true.’
Someone asked him, ‘O son of the messenger of Allah, then, who shall be the authority and Imam after you?’
He said, ‘My son Muhammad is the Imam and the authority after me. Whoever dies without knowing (acknowledging) him shall dies as an unbeliever. He will be in an occultation where the ignorant will be confused, deniers will perish, and daters will tell lies. Then, he will reappear, and as if I see white flags fluttering over his head at the hill of Kufa.’”
3. Imam Hasan Al-Askari (a) said, ‘Praise be to Allah Who did not take me out of this life until He made me see the successor after me. He is the most similar in shape and morals to the Messenger of Allah (s). Allah will protect him in his occultation and make him reappear to fill the earth with justice and fairness after it will be filled with injustice and oppression.’
4. Musa bin Ja’far al-Baghdadi narrated that he had heard Imam Abu Muhammad al-Hasan bin Ali al-Askari (a) saying, ‘As if I see that you will disagree after me on my successor. Surely, he, who believes in the Imams after the Messenger of Allah (a) but denies my son, is like one, who believes in all prophets and messengers of Allah but denies the Prophethood of the Messenger of Allah (Muhammad) (s), because the obedience of the last of us is like the obedience of the first of us, and one, who denies the last of us, is like one who denies the first of us. My son will have an occultation where people will be in doubt about it except those whom Allah preserves.’
The Imam Comforts Himself Imam Hasan Al-Askari (a) perceived from behind the unseen that he would leave this life and go near his Lord. He said to his mother, ‘In the year two hundred and sixty I shall suffer bad fever from which I shall be afflicted…’
She was distressed, and sorrow overcame her. She began crying. Imam Hasan Al-Askari (a) calmed her down saying, ‘The fate of Allah must take place. Do not worry…!’
In the year two hundred and sixty, he died as he had predicted.
Assassinating The Imam
Al-Mu’tamid, the Abbasid tyrant, could not bear Imam Hasan Al-Askari (a) any longer, for he saw and heard people everywhere full of praise for the Imam and preferring him to all the Alawids and the Abbasids. Finally, he made his mind to do away with the Imam. He assassinated him by inserting fatal poison to him. Poison reacted on his body, and he began suffering bitter and severe pains, while being patient, resorting to Allah.
The Government's Confusion
The Abbasid government was too confused when Imam Hasan Al-Askari (a) became seriously ill. Al-Mu’tamid ordered five of his trusted statesmen, among whom Nahrir was, to remain in the Imam’s house and report to him about every new happening. He also ordered a committee of physicians to test the Imam’s health day and night. After two days, he ordered the physicians not to leave the Imam alone because his state was too bad.
To the Best of Abodes
The Imam's health got worse, and the physicians were desperate of his recovery. Death began approaching him quickly. At those last moments of his life, Imam Hasan Al-Askari (a), mentioned Allah, glorified Him, and asked Him to take him nearer to Him. His lips were busy reciting verses from the Holy Qur'an. He turned towards the Qiblah, and after no long, his pure soul flew towards the Heaven surrounded by the angels of the Beneficent Lord.
It was the greatest loss Muslims suffered in that age. They lost their leader, reformer, and instructor who loved and helped their weak, poor, and orphans.
The Imam’s body was (ritually) washed, enshrouded, put in the coffin, and carried to be prayed on by Muslims. Eesa son of al-Mutawakkil led the prayer by al-Mu’tamid’s order. After the prayer, he uncovered the Imam’s face before the Hashemites, the Abbasids, army leaders, government clerks, state officials, judges, and physicians and said to them, ‘This is al-Hasan bin Ali bin Muhammad bin ar-Redha (peace be on them). He died a natural death in his bed. So-and-so of Ameerul Mo'minin’s (al-Mu’tamid) servants and trusted men, So-and-so of judges, and So-and-so of physicians were present with him.’ Then he covered his holy face.
The painful news spread everywhere in Samarra’. It was a great shock for Muslims who hurried up to the Imam’s house while crying and wailing. Government offices and all markets were closed. It was as if it was the Day of Resurrection in Samarra’.
Samarra’ did not witnessed before a day of escorting like that. Waves of human beings and flowing masses of people from all classes and trends came to escort the holy corpse of this pure Imam (a) while mentioning his virtues and favors and talking with great sorrow and regret about the great loss they were afflicted with.
In his Last Abode
The pure corpse was brought under a halo of takbir and tahlil towards the last abode. Imam Hasan Al-Askari (a) was buried in his house beside the tomb of his father Imam al-Hadi (a).
Samarra’ had two Imams from the twelve imams and leaders of Muslims, and it became at the head of the holy places in the Muslim world. It received and still receives thousands of visitors from everywhere in the world who came to visit the two holy shrines of Imam al-Hadi and Imam al-Askari (peace be on them).
Once, an-Nasir Lideenillah, the Abbasid caliph, visited the holy shrines of these two infallible imams to be blessed and close to Allah. His vizier suggested to him that he should also visit the tombs of his fathers of the Abbasid kings and he agreed. When he reached there, he found the graves dark and miserable where sweepings had accumulated and crows gathered. The vizier asked the king to take care and pay money to rebuild these graves, but the Abbasid king said,
‘How far! That is of no use.’
The vizier asked, ‘why, O Ameerul Mo'minin?’
He said, ‘Did you see the flourish of the tombs of the pure imams?’
The vizier said, ‘Yes.’
The king asked, ‘Do you know the secret behind that?’
The vizier answered, ‘No.’
An-Nasir Lideenillah said, ‘My fathers associated with Satan, and these masters associated with Allah, and all that which is for Allah remains, and all that which is for Satan perishes and disappears.’
The Alawids, the Abbasids, and Ja’far, Imam Hasan Al-Askari’s brothers stood at the tomb and the masses of people began consoling them for this painful affliction.
The Date Of His Death
Imam Hasan Al-Askari (a) departed from this world to the better world on the eighth of Rabee’ul Awwal in the year two hundred and sixty of Hijra, while he was twenty-eight years old and still in the prime of youth.
References:  Kifayat al-Athar.
 Illiyin is the highest position in the Paradise.
 Ikmaluddeen by Sheikh as-Saduq, p.216-217.
 Those who defines certain dates for the reappearance of the awaited imam (a).
 Kifayat al-Athar.
 Kifayat al-Athar, Ikmaluddeen, p.228.
 Kifayat al-Athar.
 Muhaj ad-Da’awat, p.274.
 Al-Irshad, p.383.
 Al-Irshad, p.383.
 Al-Irshad, p.383.
 Al-Irshad, p.383, Encyclopedia of al-Bustani, vol.7 p.45.
 Takbir is the saying “Allahu Akbar-Allah is great” and tahlil is the saying “la illaha illallah-there is no god but Allah”.
 Kashf al-Ghummah.
 Tareekh Baghdad, vol.7 p.366.
 Mir’at al-Jinan, vol.2 p.462, Tareekh al-Khamees, vol.2 p.343, Tareekh ibn al-Wardi, vol.1 p.325.
 Jami’ al-Akhbar, p.42, Akhbar ad-Duwal, p.117, al-Irshad, p.389.