When Ubaydullah received the letter of Yazid, he selected five hundred people from Basra, which included Abdullah bin Haris bin Nawfal, Shareek bin A’awar, both of whom were Shi’ah, and accompanied by them and Muslim bin ‘Amr Bahili and his retinue and family, left for Kufa.
(Irshad) When he reached Kufa, Ubaydullah had worn a black turban and had covered his face. People there had received news that Imam Husayn (a.s.) was due to arrive to Kufa hence they waited his arrival.
They mistook him to be Imam Husayn (a.s.), and from the midst of whichever group he passed they saluted him saying, “Welcome O son of the Prophet”! When Ubaydullah saw them rejoicing at the arrival of Imam Husayn (a.s.), he was troubled. When people started increasing, Muslim bin ‘Amr called out, “Get away, this is the commander Ubaydullah bin Ziyad.” He then reached the palace at night surrounded by a group of people who still thought that he was Imam Husayn (a.s.).
Nu’man bin Basheer shut the door on him and his comrades (mistaking him to be Imam Husayn) when one of his people called out to him to open the door. Nu’man mistaking him to be Imam Husayn (a.s.) said,
“I request you in the Name of Allah to get away from here. For by Allah, I shall not hand over the trust to you, nor do I intend fighting you.”
Ubaydullah remained silent and then came closer, when Nu’man was speaking with him while hanging from atop the balcony. Ubaydullah said,
“Open the door, you have not opened yet, and your nights have become prolonged (in which you have slept instead of governing).”
These words of Ubaydullah were heard by a man behind him, who turned to the people standing behind mistaking him to be Imam Husayn (a.s.), and said,
“O people! By Him besides Whom there is no other Deity, this is Ibn Marjanah (referring to Ubaydullah).”
Mas’oodi says that when the people recognized him, they started throwing stones at him, but he got away. (Irshad) Then Nu’man opened the door for him and he entered therein and closed the door on the people and they dispersed away.
Reference : Nafasul Mahmoom – Shaikh abbas Qummi (r.a.)