‘Alī ibn Ḥusayn (Arabic: علي بن حسين) (approximately 6 January 659 - 20 October 712) is a great-grandson of Muhammad as well as the fourth Shī‘ah Imām (the third Imām according to the Ṭayyibī [Bohra] Ismā‘ilī). His mother was Shahrbānū and his father was Ḥusayn ibn ‘Alī. His brothers include ‘Alī al-Aṣghar ibn Ḥusayn and ‘Alī al-Akbar ibn Ḥusayn. He is known as Zayn al-Abidīn "Beauty/Best of the Worshippers". He is also referred to as Imām al-Sajjad "the Prostrating Imām" and Sayyid as-Sājjadīna wa r-Rāki‘īn "Leader of Those who Prostrate and Bow".
He was beside his father right from the moment of his migration towards Karbala and followed his father. Hussain ibn Ali step by step so that, when his father asked for help on ‘Āshūrā got up to extend help to his father. Zaynab bint ‘Alī stopped him and said,
Muhammad al-Baqir (the son of Ali ibn Hussain and the fifth Shi’ah Imam) said,
As the son of Ḥusayn ibn ‘Alī, he was under great scrutiny and could not directly guide those who secretly followed the household of Muhammad. But he conveyed his understanding of the relationship between human and God by the prayers and supplications that he offered God during his extensive nighttime vigils in the mosque of the Prophet in Medina. These prayers and supplications were written down and then disseminated by his sons and the subsequent generations. Among them is the Sahifa al-Sajjadiyya, which is known as the Psalms of Islam.
He looked after and administrated hundreds of houses of the poor and hunger stricken. Daily a number of goats were slaughtered in his house and he distributed all their meat among the afflicted. He dressed the naked and the destitute ones and paid their debts and loans. But he himself took simple meals and put on simple dress.
When the nights would become dark and all the people went to sleep, ‘Alī ibn Ḥusayn would get up put the food in a sack and on his shoulder. He covered his face so that he is not recognized. Then he took that food to the houses of the inflicted and have-nots and gave it to them.
He administrated and looked after nearly a hundred guardians-less family in Medina; most of them comprised indigent, helpless and crippled, handicapped and paralytic ones. None of these families knew that ‘Alī ibn Ḥusayn was the one who managed and run their lives. But after his death, when the aids were discontinued they came to know that Ali ibn Husayn was their helper and friend.
A person came to ‘Alī ibn Ḥusayn and started addressing him with filthy and abusive language. ‘Alī ibn Ḥusayn turned his face towards him without the slightest anger and quarrel or strife and said,The man was very much ashamed and asked ‘Alī ibn Ḥusayn to pardon him.
Abu Hamza ath-Thumali, who was one of the friends of ‘Alī ibn Ḥusayn, asked his servant to briefly define the character and morals of Ali ibn Hussain. He said: "I am at his service for so many years. Whatever I saw was righteousness, piety and purity. My lord helps and assists the people and solves their problems, with all the difficulties worries and preoccupations that he himself faces." Zaid ibn Usama was lying on the deathbed. Ali ibn Hussain visited him, Zaid was weeping. When Ali ibn Husayn asked him the reason of his weeping he said, "I have to pay fifteen thousand Dinars as my loan and debt and my wealth is not so much as to pay off the debt." Ali ibn Husayn said, "Do not weep and be contented, I will pay your entire loan."
It is said that for forty years, whenever food or water was placed before him, he would weep. One day, a servant said to him, "O son of Allah's Messenger! Is it not time for your sorrow to come to an end?" He replied, "Woe upon you! Jacob the prophet had twelve sons, and God made one of them disappear. His eyes turned white from constant weeping, his head turned grey out of sorrow, and his back became bent in gloom, though his son was alive in this world. But I watched while my father, my brother, my uncle, and seventeen members of my family were slaughtered all around me. How should my sorrow come to an end?"
‘Alī ibn Ḥusayn, along with the left behind families of the fallen, was besieged by the enemy, came out on the morning of 11 Muharram, 61 AH. They had chained his hands and feet by a group of chaines called al-Jameaa "الجامعة" and placed the heads of the dead in front of him so that his sorrow and grief was increased and those chaines make a big scars and marks on his body and it was seen by his sons when they were washing before buring him and they saw these scars and marks how was it painful and how it was marked.
The family of ‘Alī ibn Ḥusayn, as against the concept a group who think they were defeated, where ever they set foot, they would announce the success of their revolution and the defeat of Yazid.