Ya‘qubi relates from Mu‘awiyah ibn Yazid ibn Mu‘awiyah, Yazid's son, that after inheriting his father's position and ascending to the caliphate, he addressed the people in this way, "And after praising Allah...
Be informed that my grandfather Mu‘awiyah ibn Abi Sufiyan had quarrelled and disputed about the caliphate with a person who was more deserving and worthy of it as regards blood relationship and proximity to the Holy Prophet (S).
Then, after him, my father got the reigns of power while he did not possess an acceptable moral character at all. In fact, he was overridden by his carnal desires." Then, Mu‘awiyah, the son of Yazid, started crying and said, "One of the hardest things for us to bear is that we know what affliction and tragedy he was caught up in, and what a terrible fate he has endorsed for himself. He killed and disregarded the honor of the Holy Prophet's (S) progeny with impunity and set the Ka‘bah on fire..."30
This historical text is excellent evidence to substantiate that Yazid had total involvement in the martyrdom of Imam al-Husayn (as). There was no one closer to Yazid than his own son, and he publicly announced that his father was Imam al-Husayn's (as) killer.
Notes:
30. Tarikh Ya‘qubi, vol. 2, p. 254.
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