After Mu’awiya died on Rajab 15, 60/April 24, 680, people gave allegiance to Yazid. He decided to take the allegiance of some of the nobles among Muslims who had previously rejected his father’s invitation for giving allegiance to him. Therefore, he wrote a letter to Walid b. ‘Utba, the governor of Medina at that time and informed him of the death of Mu’awiya and in a short letter, he wrote to him, “Take allegiance of al-Husayn b. Ali, ‘Abd Allah b. ‘Umar, ‘Abd al-Rahman b. Abi Bakr and ‘Abd Allah b. al-Zubayr by force and behead anyone of them who does not accept.”

Then, Walid received another letter from Yazid, in which he had insisted, “write the names of those who approved me and objected to me and also send to me the head of al-Husayn b. Ali (a) with the letter.” Walid consulted with Marwan b. Hakam and then sent ‘Abd Allah b. ‘Amr to Imam al-Husayn (a), ‘Abd Allah b. al-Zubayr, ‘Abd Allah b. ‘Umar, and ‘Abd al-Rahman b. Abi Bakr.

Imam (a) and 30 people of his close companions went to Dar al-’Imara (residence of emir) of Medina. Walid informed Imam (a) about the death of Mu’awiya and then read the letter of Yazid to him, in which Walid was asked to take allegiance of Imam (a) to Yazid. Imam (a) told Walid, “Will you be happy if I give allegiance to Yazid secretly? I assume you want that I give allegiance in public.” Walid said, “I have that idea.” Imam (a) said, “so, give me time until tomorrow and I will inform you of my opinion.”

The evening of the next day, the governor of Medina sent his agents to the house of Imam (a) to receive the answer of Imam (a). Imam (a) asked for the time of night as well and Walid accepted. Imam (a) decided to leave Medina

Source : wikishia