Verse 32of 85

يقَوْمِ إِنِّى أَخَافُ عَلَيْكُمْ مِّثْلَ يَوْمِ الاٌّحْزَابِ(O my people! Verily, I fear for you an end like that day (of disaster) of the groups (of old)!) meaning, those of the earlier nations who disbelieved the Messengers of Allah, such as the people of Nuh, `Ad, Thamud and the disbelieving nations who came after them, how the punishment of Allah came upon them and they had no one to protect them or ward off that punishment.

Source: Tafsir Ibn Kathir — abridged excerpt