And mention, [O Muḥammad], the brother of ʿAad,1 when he warned his people in [the region of] al-Aḥqāf - and warners had already passed on before him and after him - [saying], "Do not worship except Allāh. Indeed, I fear for you the punishment of a terrible day."2
Translation: Saheeh International (English)
1 i.e., the prophet Hūd.
2 Upon the earth. It could also refer to "a tremendous Day," i.e., that of resurrection.
O Messenger, remember Hud, the brother of Ad in lineage, when he warned his people of Allah’s punishment befalling them, when they were in their homes in Ahqaf in the south of the Arabian Peninsula, and messengers to warn their people had already passed before Hud and after him, saying to their people: “Do not worship anyone except Allah alone; do not worship anything besides Him. O people, I fear for you the punishment of a great day, which is the day of judgment”.