By Allah, the pillars of guidance have been demolished

Question: What is the meaning of Gabriel’s pbuh saying when Imam Ali pbuh was killed: “By Allah, the pillars of guidance have been demolished.”?
Are not Al-Hassan and Al-Hussein pillars of guidance, who remain alive after the murder of Imam Ali pbuh?

Answer: The first pillar is Muhammad pbuhap, the second pillar is Ali, and the third pillar is Fatima pbuh. Muhammad pbuhap is the city of knowledge, and Ali and Fatima are its door, and they three are the pillars of Truth and guidance, or the Greatest, Greatest, Greatest name (He), and its pillars (the city of divine perfections), Allah swt, and its door: Al-Rahman and Al-Raheem. If the door was any other than these two names, then punishments would have been too hard on the people of the earth, and none of them would have been saved.

And the appearance of these names amongst the creation is by Muhammad, Ali and Fatima. Muhammad is the manifestation of Allah amongst the creation, and Ali is the manifestation of Al-Rahman, and Fatima is the manifestation of Al-Raheem amongst the creation.
And by the martyrdom of the Messenger, the first pillar was demolished, and by the martydom of Fatima, the second pillar was demolished, but they remained by the remaining of the third [pillar], which is Ali pbuh. Therefore, when Ali pbuh was martyred, the third pillar was demolished; rather, the first and the second were demolished along with him. That is why Gabriel pbuh said,
“By Allah, the pillars of guidance have been demolished.”
And Al-Hassan and Al-Hussein pbut, although they remain after Imam Ali pbuh, do not represent pillars of guidance by this meaning. Therefore, the pillars of guidance are three and no more, and the Imams pbut are all pillars of guidance, but they are pillars of these [three] pillars, meaning that the Imams pbut are pillars of Muhammad, Ali and
Fatima pbut.
The Allegories – volume 1, Question 9, Ahmed Alhasan (a.s)