It is related in Biharal Anwar...
It is related in Biharal Anwar, after quoting the martyrdom of an infant child who had come out of the tent, that Imam Husayn (a.s.) turned towards the right and did not find anyone. He then turned towards the left and saw none, Imam Ali Zainul Abedeen (a.s.), who did not even have the strength to lift up a sword (due to ailment), came out. Umm Kulthum (a.s.) followed him calling out, “O dear son, return back”. He replied, “O dear Aunt!
Leave me so that I may strive for the son of the Prophet of Allah” . Imam Husayn (a.s.) saw him and said, “O Umm Kulthum! Stop him, lest the world may turn vacant of the descendants of Muhammad (S)”. Martyrdom of the suckling child (Abdullah, Ali al Asghar) His mother was Rabab, the daughter of Imru al Qays bin Adi, and her mother was Hind al Hanood.
Sayyid Ibn Tawoos says that when Imam Husayn (a.s.) saw the corpses of his youth and friends, he resolved to be martyred, and called out, “Is there anyone who could defend the family of the Prophet of Allah? Is there any monotheist who would fear Allah in respect of us? Is there any aide who could come to assist us for the sake of Allah?
Is there anyone who could rush to our aid in lieu of reward from Allah?” The voice of lamenting of the ladies arose and Imam came to the door of the tent and called for Zainab (a.s.) saying, “Give me my infant child so that I may bid him farewell”. Then he took him in his arms and bent to kiss his lips. Hurmala bin Kahil Asadi shot at arrow at the child, which pierced his neck and severed his head.
(May Allah’s Mercy and Blessings be upon him and may Allah’s curse be upon his murderer) A Poet says regarding this, “And the one who bent to kiss his child, but the arrow preceded him in kissing his neck”. Then he called out to Sayyidah Zainab (a.s.) to take him back. He filled his palm with the child’s blood and threw it towards the heavens saying, “Every hardship is easy upon me when Allah is the Beholder”.
Shaikh Mufeed says regarding the suckling child that Imam Husayn (a.s.) sat in front of the tent while Abdullah, who was an infant, was brought to him. A man from the Bani Asad killed him by shooting an arrow at him. Azdi says that Aqabah bin Basheer Asadi relates from Imam Muhammad al Baqir (a.s.) that he told me, “O Bani Asad! We hold a liability of blood among you”. I asked, “O Aba Ja’far! What sin do I share in it?