Surat Al-'Aĥqāf - سورة الأحقاف

وَاذْكُرْ أَخَا عَادٍ إِذْ أَنذَرَ قَوْمَهُ بِالْأَحْقَافِ وَقَدْ خَلَتِ النُّذُرُ مِن بَيْنِ يَدَيْهِ وَمِنْ خَلْفِهِ أَلَّا تَعْبُدُوا إِلَّا اللَّهَ إِنِّي أَخَافُ عَلَيْكُمْ عَذَابَ يَوْمٍ عَظِيمٍ

Muhsin Khan: And remember (Hud) the brother of 'Ad, when he warned his people in Al-Ahqaf (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 Allah; truly, I fear for you the torment of a mighty Day."