It is quoted by Sayyid ibn Tawoos in Malhoof that Imam Husayn (a.s.) sent a letter to a group of righteous noblemen of Basra through his retainer named Sulayman, whose agnomen was Abu Razeen, inviting them for assistance and obedience to him. Those included therein were Yazid bin Mas’ood Nahshali and Manzar bin Jarood Abadi.
Yazid bin Mas’ood then gathered the people of Bani Tameem, Bani Hanzalah and Bani Sa’ad. When they came he said, “O people of Bani Tameem! What is my position and descent in your eyes”? They replied, “It is fair. By Allah! You are a support of our backs and the prime of nobility, and hold a place in noble presence and you take lead in it.” Then he said, “I have gathered all of you here so that I may ask your opinion regarding a matter and invite your assistance for it.” They said, “By Allah! We are your well-wishers and we shall not be reluctant to counsel you sincerely. You may say, so that we may know what it is.”
Yazid bin Mas’ood said, “Mu’awiyah has died, and we do not grieve nor regret his death, because the doors of injustice and tyranny have cracked and the pillars of oppression have been given a severe blow. He has made innovations in the form of (demanding) allegiance for his son (Yazid) and he was adamant about it, when how far from right is it what he had decided. He endeavored but was weakened and he asked for counsel and opinion from his friends, but they betrayed him.
Then his son Yazid who drinks wine and is wicked has arisen and has claimed to be the Caliph of the Muslims. He rules over them without their consent in spite of being an ignorant and foolish man, he cannot even recognize his own footsteps. I swear by Allah, that fighting Yazid is more worthy than fighting with the polytheists. And this is Husayn bin Ali, the grandson of Prophet Muhammad (S).
He is of genuine dignity, an honest counselor, a great intellectual, and is more worthy and rightful for the Caliphate. For he is an antecedent among the emigrants, a senior, and foremost in Religion, he is attached in proximity to the Prophet. He is affectionate towards the young and sympathetic towards the elders while being kind to others. He is a thorough Leader, and Paradise is attained through his medium, while he propagates through preaching and counsel. Hence do not close your eyes against the Light of Truth and do not fall into the pit of falsehood.
Sakhr bin Qays misled you on the day of (the battle of) Jamal and disgraced you, hence wash off the stains of disgrace from yourselves by assisting the grandson of the Prophet. By Allah! None will withhold their hands from assisting him except that their progeny will be humiliated, deprived and abandoned. I have now worn the helmet for the battle and have fastened the armor. For the one who is not killed will ultimately die, and the one who flees from it will not escape it. Thus answer me well, may Allah’s blessings be upon you.”
Hearing this the Bani Hanzalah said, “O Aba Khalid! (referring to Yazid bin Mas’ood) We are the quiver of your arrows and the champions of the clan. If you hurl us (towards the enemy) we shall fall upon the target, and if you accompany us in the battlefield you shall emerge a victor. If you enter the depths of the sea we too shall accompany you, and turn to whichever side you turn to. We shall defend you with our swords and our bodies shall be your shield. We are at your disposal whenever you need us.”
Then Bani Sa’ad bin Yazid said, “O Aba Khalid! The most abhorred thing in our sight is opposing you and failing to accept your command. Verily Sakhr bin Qays had forbade us to fight (on the day of the battle of Jamal) and we were pleased by this act of ours and our dignity remained intact. You may give us respite so that we may counsel among ourselves and let you know our opinions regarding it.”
While the Bani Amir bin Tameem said, “O Aba Khalid! We are the children of your father and your confederates. If you are displeased, we shall not remain satisfied, and if you leave, we shall not linger behind. Hence command us so that we may respond, and call us so that we may obey you. Verily command is with you.”
Then he told the Bani Sa’ad, “O Bani Sa’ad! By Allah! Then if you are in doubt and you shall side with the Bani Umayyah (and fail to assist Husayn), Allah will never lift the sword away from your necks, while you still hold your swords.”
Then he (Yazid bin Mas’ood) wrote a reply to Imam Husayn (a.s.), “Now then! We have received you letter and have pondered over that which you have invited, that we may have our share of obedience to you and we may attain the excellence of assisting you. Allah never lets the earth to remain empty of His Vicegerent, who is benevolent and the guide to the path of salvation. Verily you are Allah’s proof over His creation and His trust upon the earth. You are a branch of the olive tree of Muhammad (S). He was the origin while you are the branch. Hasten to us with felicitations, for I have brought the necks of Bani Tameem under your command and they shall excel each other in your obedience like the thirsty Lions who make haste to drink water. Besides I have brought the Bani Sa’ad under your submission and have washed the filth from their hearts with (rain) water falling from the clouds.”
When Imam Husayn (a.s.) read the contents of the letter he said,
“What else do you desire. May Allah grant you security on the day of fright (Qiyamah) and quench your thirst on the day of extreme thirst and endear you.”
When Yazid bin Mas’ood was just preparing to proceed towards the Imam, he received the news of his martyrdom. Hence he lamented over the loss of this grace (of Martyrdom).
Reference : Nafasul Mahmoom – Shaikh abbas Qummi (r.a.)