In the twenty fifth of the month of Shawwal in the year 148 AH, the Imam As-Sadeq (peace be upon him) was martyred at the age of 65 years, as his birth was in the seventh of Rabi' Awal 83 AH.
Imam Ja'far As-Sadeq (peace be upon him) is the son of Imam Mohammed Al-Baqer (peace be upon him), his mother was Farwa daughter of Al-Qasem son of Mohammed Ibnu Abi Bakr, her nickname was "Al-Mukarramah". He (peace be upon him) has lived a difficult period at the time of the Umayyad transgressing rule, and faced different kinds of injustice and cunning, but it was the Abbasids in the person of Abu Ja'far Al-Mansur, who assassinated by poison Imam As-Sadeq (peace be upon him) in the twenty fifth of Shawwal of the year 148 AH.
The period of his Imamate coincided with the most revolutionary and eventful era of Islamic history which saw the downfall of the Umayyad Empire and the rise of the Abbasid caliphate. The internal wars and political upheavals were bringing about speedy reshufflements in government. Thus, Imam As-Sadeq (peace be upon him) witnessed the reigns of various kings starting from Abdu 'l-Malik down to the Umayyad ruler Marwan al-Himar. He (peace be upon him) further survived till the time of Abu 'l-Abbas al-Saffah and al-Mansur among the Abbasids. It was due to the political strife between two groups viz., the Umayyads and Abbasids for power that Imam (peace be upon him) was left alone undisturbed to carry out his devotional duties and peacefully carry on his mission to propagate Islam and spreading the teachings of the Holy Prophet (prayers and Allah's peace be upon him and upon his holy household).
In the last days of the Umayyad rule, their Empire was tottering and was on the verge of collapse, and a most chaotic and demoralized state of affairs prevailed throughout the Islamic State. The Abbasids exploited such an opportunity and availing themselves of this political instability, assumed the title of "Avengers of Banu Hashim". They pretended to have stood for the cause of taking revenge on the Umayyads for shedding the innocent blood of the Imam Al-Hussayn (peace be upon him). The common people who were groaning under the yoke of the Umayyads were fed up with their atrocities and were secretly yearning for the progeny of the Holy Prophet (prayers and Allah's peace be upon him and upon his holy household) to take power. They realized that if the leadership went to the Ahl Al-Bayt (peace be upon them), who were its legitimate heir, the prestige of Islam would be enhanced and the Prophet's mission would be genuinely propagated. However, a group of the Abbasids secretly dedicated their lives to a campaign for seizing power from the hands of the Umayyads on the pretext that they were seizing it only to surrender it to the Banu Hashim. Actually, they were plotting for their own ends. The common people were thus deceived into supporting them and when these Abbasids did succeed in snatching the power from the Umayyads, they tuned against the Ahl Al-Bayt (peace be upon them).
The Imam (peace be upon him) thus took advantage of the occasion to propagate the religious sciences until the very end of his Imamate. He instructed many scholars in different fields of the intellectual and transmitted sciences. It is said that his classes and sessions of instructions produced four thousand scholars of hadith and other sciences. The great Imam As-Sadeq (peace be upon him) was righteous, truthful, and of great importance. He was surnamed "As-Sadeq" because his speech was truthful. And his outstanding merit was more famous than to be mentioned.
When al-Mansour al-Dawaniqi decided to assassinate the Imam, he sent a killing poison to his agent in Madina to feed it to the Imam, once he (peace be upon him) drunk it, he felt a severe pain and died poisoned.
His son Imam Musa al-Kadhem (peace be upon him) was the responsible to prepare the funeral of the Imam as-Sadeq (peace be upon him) and then led the funeral prayer, to be buried near his grandfather Imam Zayn al-'Abideen and his father Mohamad al-Baqer (peace be upon both of them) in the Baqi' cemetery, while people of Madina were crying for their great loss.