Al-Ahqaf 46:21

Remember [Hūd][8] the brother of ‘Ād, when he warned his people in the [land of] sand dunes[9] – and indeed there came warners before him and after him – [saying], “Worship none but Allah. Indeed, I fear for you the punishment of a horrible day.”

[8] i.e., Prophet Hūd.
[9] The people of ‘Ād were the inhabitants of the sand dunes (sand hills) in the southern part of Arabia.

And mention, [O Muḥammad], the brother of ʿAad,[1484] 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."[1485]

[1484] i.e., the prophet Hūd.
[1485] Upon the earth. It could also refer to "a tremendous Day," i.e., that of resurrection.

21. And remember (Hûd) the brother of ‘Âd, when he warned his people in Al-Ahqâf (the curved sand-hills in the southern part of Arabian Peninsula). And surely, there have passed away warners before him and after him (saying): "Worship none but Allâh; truly, I fear for you the torment of a mighty Day (i.e. the Day of Resurrection)."

And make mention (O Muhammad) of the brother of A'ad when he warned his folk among the wind-curved sandhills - and verily warners came and went before and after him - saying: Serve none but Allah. Lo! I fear for you the doom of a tremendous Day.