Hadhrat Qasim was the youngest son of Imam Hassan(A). Qasim was born in 47 A.H., three years before his father was martyred. When imam Hussain prepared to leave Madina in the month of Rajab 60 A.H. Qasim mother Umme-e-Farwa asked Imam Hussain to take her and Qasim with him. imam Hussain agreed. Hadhrat Qasim, although only 13 years old, had, like his cousins Aun and Muhammad, learnt fencing from Hadhrat Abbas and Hadhrat Ali Akber. Hadhrat Abbas was very fond of Hadhrat Qasim.

On the night before Ashura when Imam Hussain was passing by Umm-e-Farwa’s tent he heard Qasim say to his mother, “Mother, tomorrow Uncle Abbas, Ali Akber and I will defend Imam Hussain. Mother, if I get killed please do not weep for me.” Umm-e-Farwa replied, “My son although I dearly love you, I shall not weep for you. Nothing will make me prouder than to see my son give his life for Islam”. When Imam Hussain heard this conversation he prayed to Allah to bless Hadhrat Qasim and Umm-e-Farwa.

On Ashura day after Aun and Muhammad had fallen in the battlefield, Hadhrat Qasim came to imam Hussain and begged for permission to go and fight. Twice Imam Hussain refused saying “Qasim you are young and your mother’s only son”. Hadhrat Qasim was very disappointed. He went to his mother. When she saw her son so disappointed she remembered that just before he died, Imam Hassan had written a letter, given it to Umm-e-Farwa saying ,”If ever you find Qasim in difficulty, give him this letter.” She gave Hadhrat Qasim the letter. In the letter it was written, “My son Qasim, a day will come when my brother Hussain will be facing an enemy army of tens of thousands. That will be the day when Islam will need to be saved by sacrifice. You must represent me on that day.”

Hadhrat Qasim read the letter. He smiled. He rushed to imam and gave him the letter. After reading the letter Imam Hussain said, “O my brother’s son, how can I stop you from doing what your father wanted you to do. Bismillah, go. Allah be with you”.   Imam Hussain tied imam Hassan’s turban on the head of Hadhrat Qasim and helped him mount his horse. As Qasim was riding out, Imam Hussain said “Inna Lilla-hi Wa Inna Ilai-hi Raji’oon”. Hadhrat Qasim said “O my uncle - Do not be upset. I do not fear death. Death for Islam will be sweeter for me than honey”.
 
Hadhrat Qasim came to the battle field. He was a very handsome boy. When the enemy saw him, they began to murmur, “How can we kill someone whose face is shining like moon?”  In a loud and a clear voice Hadhrat Qasim introduced himself and cried out a challenge for single combat. He killed several famous warriors who came forward. Every time he felled an enemy Hadhrat Qasim would stand on his stirrups, look behind and wave to Hadhrat Abbas, just as a pupil would seek approval of his teacher on any assignment, Hadhrat Abbas would proudly wave back. When the enemy saw his bravery and realized that they could not possibly over power him in single combats, they came from behind and one of them hit Hadhrat Qasim on the head with a sword.

Hadhrat Qasim tried to go on fighting but alas he was so young and he was so very thirsty! He fell from his horse crying out, “YA AMMAHO, ACCEPT MY LAST SALAAMS.” Imam Hussain and Hadhrat Abbas rode out. The soldiers tried to stop them, when finally they came to where Hadhrat Qasim had fallen they saw a dreadful sight!! Hadhrat Qasim’s body had been trampled by the horses of the soldiers who had tried to stop Imam Hussain and Hadhrat Abbas. Hadhrat Abbas was so angry when he saw this that h e began to shake with fury. He took out his sword and wanted to attack the enemy. Imam Hussain restrained him saying “Abbas, have patience, dear brother. Do not give them an excuse for saying that we attacked them first”.

Was Qasim body carried to the camp to his mother? This is not very clear. It is reported, however, that Imam Hussain took off his abaa, spread it on to the ground, gathered the pieces from the ground as one gathers flowers from a garden!