On the day of 'Ashura, 'Umar Ibn Sa'd lined up his army and appointed commanders for all sections. He appointed al-Hurr Ibn Yazid al-Riyahi as the commander of Banu Tamim and Banu Hamdan. After military arrangements, the army prepared to fight Imam al-Hussayn (peace be upon him) and his companions.
When noticed the serious will of 'Umar Ibn Sa'd to confront Imam al-Hussayn (peace be upon him), Hurr went to him and asked: "do you really want to fight with this man (Imam al-Hussayn (peace be upon him))?" Umar replied: "yes, by God I will start a war the lightest [part] of which is dropping heads and chopping hands." Al-Hurr asked: "weren't his suggestions good enough for you?" Umar Ibn Sa'd replied: had it been up to me, I would have accepted, yet the commander (Ibn Ziyad) did not accept."
Then al-Hurr distanced from 'Umar Ibn Sa'd and went to a corner of the army and little by little, got close to the other side. Muhajir Ibn Aws –a member in Umar's army- asked al-Hurr: "Do you want to attack?" Al-Hurr did not reply and was shaking. Muhajir became suspicious and said: "by God I have never seen you in any war like this, if I was asked who the bravest man of Kufa was, certainly I wouldn't miss your name. Now, what is this state I see you in?" al-Hurr said: "truly I see myself between paradise and hellfire; and by God, if I get torn apart and burned, I will not choose anything but paradise." Upon saying this, al-Hurr directed his horse toward the campsite of Imam al-Hussayn (peace be upon him).
It is narrated that he went to Imam Hussayn (peace be upon him) and said, “May I be your ransom O son of the Prophet of Allah! I am the one who had stopped you from returning back and had accompanied you all along and had forced you to alight here. But I had not known that these people would directly refuse your proposal and bring you to this present state. By Allah! If I had known that they would do to you such, I would not have undertaken that what I have done. Hence now I apologize to Allah regarding that what I have done, then do you think that my repentance would be accepted”?
Imam Hussayn (peace be upon him) replied,
“May Allah accept your repentance! Thus alight from your horse.”
Hurr replied, “It is better for me to be mounted and serve you and fight with them, thus ultimately I will have to alight from my horse (when I am wounded).” Then Imam replied,
“May your Lord have mercy upon you, do as you desire.”
Then he stood in front of Imam Hussayn (peace be upon him) and said, “O Kufans! May your mothers be deprived of you! You invited the righteous slave of Allah, then when he came to you, you handed him over to the enemy, when you had intended to defend him with your lives? Then now you have begun to fight him so as to kill him. You have taken hold of him and seized his collar, and have surrounded him from all sides so that he may not be able to escape to the vast towns of Allah.
He is now left as a prisoner amongst you, then he cannot benefit himself nor can he ward off the evil from it. Then you have stopped him, along with his women-folk, his children and family, from the waters of Euphrates, which is open for the Jews, Christians and Sabians, and the pigs and dogs of Iraq roll therein, while they would perish because of thirst? How badly have you behaved with the Progeny of Mohammad (Allah’s prayers be upon him and upon his holy Household) after his death. May Allah not quench your thirst on the day of extreme thirst (Qiyamah)!” Hearing this some of the soldiers attacked him and started shooting arrows at him, then Hurr came and stood in front of Imam Hussayn (peace be upon him)
Imam al-Hussayn (peace be upon him) requested God's forgiveness for him and said: "You are hurr (a freeman) in this world and in the hereafter."
Shortly after joining Imam's camp, al-Hurr went to the battlefield and after his word with 'Umar Ibn Sa'd and his army. The narrator says that Hurr started reciting the following Rajaz: “I have sworn not to be killed until I do not kill, and I shall not be wounded except by advancing further, I will attack them with a sharp-edged sword, I shall not retreat back nor will I flee (from the battlefield).”
Furthermore he recited the following couplets: “I am Hurr, a host to the guest, I strike your necks with a swift sword, in defense of the one who has alighted at the ground of Kheef (in Mina), while I do not regret over it.”
He held such a sword in his hand whose edge was raining death. It is as if Ibn Mu’taz says about him, “I possess a sword which radiates death, then it is not unsheathed, except that it starts spilling the blood.”
Hurr, along with his companion Zuhayr Ibn Qayn, attacked obviously. If while fighting, one of them would get surrounded by the enemies, the other would come to his defense and rescue him. After several rounds of combat, he was martyred. He fought bravely and even though his horse was injured and was bleeding from forehead and ears, he kept reciting Rajaz and attacking the enemy on the same horse. He killed more than forty members of Umar's army. Then the infantry part of the army rushed to him at once and martyred him. It's been reported that two individuals killed him, Ayyub b. Musarrah and a horseman from Kufa.
Other companions brought the body of al-Hurr, Imam al-Hussayn (peace be upon him) sat beside his body, wiped off the blood on his face and said: "you are [truly] hurr (a freeman), like the way your mother has named you, you are a freeman both in this world and in the hereafter."
Then he recited the following couplets: “What a best Hurr is the Hurr of Bani Riyah, and the best Hurr during the exchange of spears, the best Hurr who was generous with regard to his life when Hussayn called out in the morning.”