Name: al-Hasan.
Title: al-Mujtaba.
Agnomen: Abu Muhammad.
Father’s name: Ali Amir al-Mu’minin.
Mother’s name: Fatimah (daughter of the Holy Prophet).
Birth: In Medina on Tuesday, 15th Ramadan 3 AH.
Death: Died at the age of 46, in Medina on Thursday, 28^th Safar 50 AH; buried in Jannatu ‘l-Baqi’, in Medina.

Remembrance of Allah:

The Holy Imam devoted himself to prayers in such abundance, that all the limbs employed in prostration bore scars and impressions of his sajdah (prostration). Most of the nights were spent on the prayer-carpet. The sense of his absorption and humiliation in prayers to Allah were in such earnest that he would shed tears profusely out of fear of Allah. While performing ablution, he trembled with the fear of Allah and his face grew pale at the time of prayers. His earnest meditation in the offering of prayers and his extreme absorption in communion with Allah would render him entirely unconscious of his environments.

His Piousness and Contentment:

Imam Hasan had the worldly possessions at his disposal and could have well enjoyed a luxurious life, but he utilized all of it in the betterment of the condition of the poor. He was so courteous and humble that he never hesitated to sit along with the beggars in the lanes and on the thoroughfares of Medina to reply to some of their religious queries. Through his cordial attitude and hospitality he never let the poor and the humble feel inferior to him when they visited his abode.

Imamate:

The martyrdom of Imam Ali on the 21st Ramadan marked the inception of Imam Hasan’s Imamate. The majority of Muslims pledged their allegiance to him and finalized the formality of bay’ah (oath of allegiance). No sooner had he taken the reins of leadership into his hands than he had to meet the challenge of Mu’awiyah, the Governor of Syria, who declared a war against him. In compliance with the Will of Allah and with a view to refrain from causing the massacre of Muslims however, he entered into a piece treaty with Mu’awiyah on terms (though not totally respected and carried out by Mu’awiyah), yet saved Islam and stopped a civil war. But this peace treaty was never meant as surrender by him of the permanent leadership to Mu’awiyah. It was meant only as an interim transfer of the administration of the Islamic kingdom, subject to the condition that the administration would be surrendered back to Imam Hasan after Mu’awiya’s death and then it would in turn be inherited by Imam Husayn. Having relieved himself of the administrative responsibilities, Imam Hasan kept the religious leadership with himself and devoted his life to the propagation of Islam and the teachings of the Holy Prophet in Medina.

Mu’awiyah’s malice against Imam Hasan led him to conspire with the Imam’s wife Ja’dah, the daughter of Ash’ath. She was made to give the Imam some poison which affected his liver. Imam Hasan thus succumbed to Mu’awiyah’s fatal mischief and attained his martyrdom on 28th Safar 50 AH. His funeral was attended by Imam Husayn and the members of the Hashimite family. His bier while being taken for burial to the Holy Prophet’s tomb was shot at with arrows by his enemies, (under direct supervision and consent of A’ishah), and it had to be diverted for burial to the Jannatu’l-Baqi` at Medina. His tomb was demolished along with others on 8th Shawwal 1344 (21st April 1926) by the Saudi rulers when they came to power in Hijaz.

The terms of the peace treaty were soon violated, but earned only a short-lived glory for Mu’awiyah. Its aftermath proved disastrous and doomed the fate of his son Yazid and dealt a fatal blow to the entire family of Umayyads. After the death of Mu’awiyah, Imam Husayn emerged as the insurmountable mountain of truth and determination. In the gruesome tragedy of Karbala’, by sheer force of numbers, and by isolating the seventy-two members of Imam Husayn’s party and stopping them from even getting water to drink for three days, Yazid succeeded in annihilating the seventy-two persons including members of the Imam’s family who were with him.

This dastardly success of Yazid was, however, short-lived. The Muslims turned against him on learning of the heinous act he had committed and this resulted in the downfall of Yazid and the extinction of the Umayyad power from the face of the earth.

Al-Imam al-Hasan, peace be on him, said:

“Opportunity is something which is quick to vanish and late to return”.

Reference: https://www.al-islam.org/brief-history-fourteen-infallibles/fourth-infallible-second-imam