Imam Zayn al-Abidin (sa), was ill, according to some had the stomach illness, others talk about an injury.
Imam Zayn al-Abidin (as) was involved in a skirmish when fighting for access to the water or to the river Euphrates and he was injured.
And it seems possibly, if we were to reconcile the two opinions about an ache in the stomach and the skirmish, that there may have been an injury there - where he was recovering from the injury and was not able to participate on the plains of Karbala with his sword on the 10th of Muharram.
Allah is the best of planners.
He wanted to protect the Imam (as) in order to ensure that he would look after and safeguard the Message of his great grandfather, Rasul Allah, salla Allahu alayhi wa alih.
Imam al-Sajjad (as) after tragedy of Karbala
They were wondering how Islam was saved.
When time for Azan came and the Moazzin screamed from the minaret "I bear witness that Muhammad is the messenger of Allah", Imam (as) shouted to Yazid, this is the way Islam was saved.
People would have forgotten the name of Muhammad as the Messenger of Allah if his grandson would not have shown the world that you were a ruler by default.
Yazid ordered his swordsman to kill this young man, but by the intervention of his aunt Zainab his life was spared.
He remained in prison for one year with the whole family. There was turmoil in all parts of the Islamic empire on this brutal killing.
In the end Yazid was afraid that if he kept the family of the Prophet in prison any longer, he would lose his kingdom. So, he sent orders to bring the family before him and told him that he was releasing them.
He also asked what they wish to do now.
In reply to this His aunt Zainab (sa) said that they would wish to hold a gathering in Damascus so that she can tell the people what happened in Karbala.
Yazid agreed and the first Majlis was held in Damascus.
In this Majlis most of the women of Damascus took part who were secretly following the path of Ahlulbayt (as) which included Yazid"s wife Hind.
Then they all returned to Karbala to pay homage over the graves of their beloved father, uncles and brothers.
It was on the 20th of the month of Safar 62 Hijri that they arrived back in Karbala. The first Majlis of Arbaeen was held in Karbala in which his aunt Zainab (sa) and all the surviving family attended.
It was at that time that one of the companions of the Prophet Jabir Ibn Abullah Ansari visited the grave of Imam Hussain (as) who later narrated the whole story of Karbala to many of his listeners in Madina and many other towns he visited.
The message of Imam Hussain (as) was spreading from town to town and from country to country.
The whole family then returned to Madina except the wife of Imam Hussain (as). Her name was Umm-e-Rabab.
She said that she would not return back home, for her home was here where her husband lay buried. She stayed in Karbala until she died a few years later.
A small town flourished for the up keeps of pilgrims who began to visit the grave of Hussain (as) and all the martyrs of Karbala.