Bukhari

Hadith Commentary:
In the verse, by "leaders of disbelief" (a'immat al-kufr) are meant Abu Sufyan, Abu Jahl, Utbah, Suhayl ibn Amr, and others.
The meaning of Hudhayfah radi Allahu anhu is that all these people have been killed or have died, and only three individuals from among them remain alive—namely, Abu Sufyan, Suhayl, and one other person.
Although at that time Abu Sufyan and Suhayl had become Muslims, at the time of the revelation of the verse, these people were among the leaders of disbelief, by which are meant the chiefs of the armies of the disbelievers.
Hudhayfah radi Allahu anhu was a confidant of the Messenger sallallahu alayhi wa sallam.
He would have known this.
Hafiz (Ibn Hajar) rahimahullah states that the names of the four mentioned hypocrites have not become known to me.
(Fath al-Bari)

Hadith Commentary:
➊
Imam Ibn Jarir has clarified in his Tafsir that Hudhayfah (radi Allahu anhu) recited ﴿فَقَاتِلُوا أَئِمَّةَ الْكُفْرِ﴾ and said that the opportunity to fight the referents of this verse among the people did not arise.
Hafiz Ibn Hajar (rahimahullah) writes:
“That fighting was not undertaken against them because the two conditions for fighting them were not fulfilled, as they had accepted Islam.”
(Fath al-Bari: 8/410)
At the time of the revelation of the verse, the leaders of disbelief (a’immah al-kufr) who were alive were Abu Sufyan ibn Harb and Suhayl ibn Amr (radi Allahu anhuma). Both of these individuals had become Muslim, and Islam had forgiven their previous errors, so the opportunity to fight them did not arise.

➋
Hudhayfah (radi Allahu anhu) was the keeper of secrets.
He had knowledge of the hypocrites (munafiqun) and the leaders of disbelief (a’immah al-kufr).
Therefore, he clarified in the hadith that the opportunity to fight the leaders of disbelief did not arise.

➌
The purpose of the Bedouin’s (a‘rabi’s) question was that if three from the leaders of disbelief and four from the hypocrites remained, then so few people could not carry out acts like banditry, etc.
Then who are these people?
Hudhayfah (radi Allahu anhu) explained that these could be sinners and transgressors (fasiq wa fajir), but they are not the leaders of disbelief or hypocrites.
Among these hypocrites, one is so elderly that if he drinks cold water, he does not feel its coolness—that is, Allah Ta‘ala has punished him in this world such that he does not experience the pleasure or coolness of water.
And Allah knows best.

➍
From this verse, it is also understood that if the people of dhimmah (ahl al-dhimmah) living under an Islamic government mock or deride the religion of Islam, then their covenant is nullified and it becomes the duty of the Islamic government to suppress them.
Similarly, any dhimmi who insults the Messenger of Allah (sallallahu alayhi wa sallam), mocks him, or shows disrespect towards his status is also liable to be killed, because this is one of the worst forms of derision against the religion.
And Allah knows best.