“O Messenger of Allah, what should we say?”
He answered,

“Say: ḥasbunā Allāh wa niʿma al-wakīl (Allah is sufficient for us and what an excellent Trustee).” (1)

Abū Yaʿlā al-Mawṣilī also said in the Musnad of Abū Hurayrah—by way of Abū Ṣāliḥ from Abū Hurayrah: Abū Ṭālib ʿAbd al-Jabbār ibn ʿĀṣim (2) narrated to us; Mūsā ibn Aʿyan al-Ḥarrānī told me, from al-Aʿmash, from Abū Ṣāliḥ, from Abū Hurayrah—and from ʿImrān, from ʿAṭiyyah, from Abū Saʿīd, who said:
The Messenger of Allah ﷺ said, “How can I enjoy myself—or how will you? (Abū Ṭālib was uncertain)—when the bearer of the Horn has already placed the horn to his mouth, has inclined his ear and bowed his forehead, waiting to be ordered so that he may blow?”
They asked, “O Messenger of Allah, what should we say?”
He replied, “Say: ḥasbunā Allāh wa niʿma al-wakīl, ʿalā Allāh tawakkalnā (Allah is sufficient for us and what an excellent Trustee; upon Allah we rely).”

Imam Aḥmad said: Abū Muʿāwiyah narrated to us; al-Aʿmash, from Saʿd al-Ṭāʾī, from ʿAṭiyyah al-ʿAwfī, from Abū Saʿīd al-Khudrī, who said:
The Messenger of Allah ﷺ mentioned the bearer of the Horn and said, “On his right is Jibrīl and on his left is Mīkāʾīl (peace be upon them).” (3)

Ibn Mājah said: Abū Bakr ibn Abī Shaybah related to us; ʿAbbād ibn al-ʿAwwām, from Ḥajjāj, from ʿAṭiyyah, from Abū Saʿīd, who said:
The Messenger of Allah ﷺ said, “The two bearers of the Horn have— or, in their hands are—two horns, keeping their gaze fixed, waiting for the command.” (4)

Imam Aḥmad likewise said: Yaḥyā ibn Saʿīd related to us, from al-Taymī, from Aslam, from Abū Murayyah (5) from the Prophet ﷺ—or from ʿAbd Allah ibn ʿAmr, from the Prophet ﷺ—who said:
“The two trumpet-blowers are in the second heaven; the head of one of them is in the east and his feet in the west”—or he said: “his head is in the west and his feet in the east—waiting for the moment they will be commanded. Then they will blow into the Horn, and they will blow.”
This wording is unique to Aḥmad. That Abū Murayyah is ʿAbd Allah ibn ʿAmr al-ʿIjlī, who is not well known. (6)

It is possible that these two angels are: one of them Isrāfīl, who will blow into the Horn—as will be explained at length in the hadith of the Horn—and the other the one who strikes the nāqūr. It may also be that ṣūr and nāqūr are generic terms covering many individuals, or that the definite article in them denotes a specific instance, each of the two having subordinates who do as they do. Allah knows best.