Bukhari

Hadith Commentary:
And all of them turned their faces towards you.
This is precisely the meaning of the chapter.
The foremost purpose of the sermon (khutbah) is that the congregation should listen to the address of the imam with full attention, internalize it, and resolve to act upon it.
From this, it is also evident that the imam’s address should be in such a manner that the listeners can understand it.
From this, the permissibility of delivering the sermon (khutbah) in the mother tongue of the listeners is also established; that is, the verses and hadiths should be recited and then explained in the mother tongue of the listeners, and the congregation should turn towards the imam and listen with full attention.

Hadith Commentary:
(1)
This hadith is part of a lengthy narration which Imam Bukhari rahimahullah has mentioned in the Book of Zakat, the Book of Jihad, and the Book of Heart-Softening Narrations (Riqaq). Here, the wording is "he sat down," whereas in another narration it is stated that he stood on the pulpit. (Sahih al-Bukhari, al-Jihad wal-Siyar, Hadith: 2842) Hafiz Ibn Hajar rahimahullah has written that Imam Bukhari rahimahullah deduced from the aforementioned hadith that the Companions radi Allahu anhum sitting attentively around the Messenger of Allah sallallahu alayhi wa sallam and listening to his sermon indicates that they were all focused on him. (Thus, it is understood that he too was facing towards them.) Imam Tirmidhi rahimahullah states that nothing is established explicitly from the Messenger of Allah sallallahu alayhi wa sallam regarding this matter.
(2)
It appears that this refers to a sermon other than the Friday sermon, because it is established that during the Friday sermon, he would stand. When the Companions radi Allahu anhum were so attentive outside of the Friday sermon, then during the Friday sermon their attentiveness would be even greater, since there is a command to remain silent and listen attentively to it. (Fath al-Bari: 2/517)
(3)
In our mosques, along with the formation of rows, facing the imam also occurs; however, in the Prophet’s Mosque (Masjid Nabawi), this is necessary because there is some distance between the mihrab and the pulpit, and there are some rows in between. There, it is necessary to face the imam, because the imam is behind them. Those sitting in the front rows should sit facing the imam, even if in doing so their backs are turned to the qiblah.