Bukhari

Hadith Commentary:
Sa’d (radi Allahu anhu) thought that in the Battle of Ahzab, the disbelievers of Quraysh had exerted their full strength, and in the end, they fled. Therefore, now the Quraysh no longer have the strength to fight.
Perhaps now there will be no more war between us and them.

Hadith Commentary:
Hazrat Sa’d bin Mu’adh radi Allahu anhu thought that in the Battle of Ahzab, the entire strength of the disbelievers of Quraysh had been exhausted; after all, they had fled, so perhaps now the Quraysh no longer had the strength to fight, and now there would be no more war between us and them.

From the narration of Hazrat Aban, it is understood that by this, the disbelievers of Quraysh are meant, not Banu Qurayzah, as is further clarified in another narration, in which Hazrat Sa’d radi Allahu anhu supplicated thus:
O Allah! If anything remains of the battles with Quraysh, then let me remain alive.
But if You have ended the war between us and them, then grant me martyrdom in this state of illness. Accordingly, the wound he had sustained—caused by an arrow striking the akhil vein—began to bleed, until he passed away.
(Sahih al-Bukhari, al-Maghazi, Hadith: 4122)

By this, the Quraysh are meant, because it was they who had forced the Messenger of Allah sallallahu alayhi wa sallam to leave Makkah al-Mukarramah.
Banu Qurayzah are not meant by this, as some commentators have understood.
And Allah knows best.
(Fath al-Bari: 7/286.)