Is the one who declares Umar ibn al-Khattab a disbeliever himself a disbeliever? And why?

The principle is: whoever declares a Muslim a disbeliever has himself disbelieved, whoever declares a Muslim a disbeliever.

He has disbelieved, and when Imam Ahmad was asked about a man who insults Abu Bakr and Umar, he said: That one is a heretic.

Insulting Abu Bakr and Umar, he says this is a heretic, so yes, whoever declares Umar a disbeliever is a disbeliever.

And whoever declares Ali a disbeliever is a disbeliever, and whoever declares Uthman a disbeliever is a disbeliever, and whoever declares Abu Bakr a disbeliever is a disbeliever.

But the one who insults them without declaring them disbelievers, this is what Imam Malik spoke about, he said: this one is corrupt, wicked, he should be flogged and disciplined.

But as for declaring them disbelievers, yes, whoever declares them disbelievers is himself a disbeliever.