Ali Ibn Al Husayn, known as Imam al-Sajjad and Zayn al-Abidin is the fourth Imam of Shia Muslims. The period of his imamate was 34 years. He (a) was present in the Battle of Karbala but did not participate in the battle because of sickness and was not martyred. He (a) was taken captive to Kufa and Damascus together with other captives of Karbala. His speech at the presence of Umayyad caliphs created awareness among people about the position of the Ahl al-Bayt (a). After being released, he (a) stayed in Medina until the end of his life. The event of Harra, Tawwabun movement and the uprising of Mukhtar happened at his time, however there is no reliable report of his opinions about them.

Al-Sahifa al-Sajjadiyya is a compilation of his supplications which reflect the picture of the society that day and the true path of life through the education of the religion and the Qur’an and purification of souls and connecting souls to God. Risalat al-huquq (Treatise on Rights) is his another work which is a short treatise containing duties a human being have.

Imam Zayn al-Abidin (a) was poisoned and martyred by the order of Walid b. ‘Abd al-Malik. He (a) was buried in al-Baqi’ cemetery beside his uncle Imam al-Hasan al-Mujtaba (a).

Al-Zahri said, “I found none of Hashemites greater or more knowledgeable than him in fiqh.” Al-Shafi’i said, “He (a) was the most knowledgeable in fiqh in Medina.” And al-Jahiz said, “I saw no one have any doubt about his merits or about his superiority.”