وَاذكُر أَخا عادٍ إِذ أَنذَرَ قَومَهُ بِالأَحقافِ وَقَد خَلَتِ النُّذُرُ مِن بَينِ يَدَيهِ وَمِن خَلفِهِ أَلّا تَعبُدوا إِلَّا اللَّهَ إِنّي أَخافُ عَلَيكُم عَذابَ يَومٍ عَظيمٍ

And mention, [O Muhammad], the brother of 'Aad, when he warned his people in the [region of] al-Ahqaf - and warners had already passed on before him and after him - [saying], "Do not worship except Allah. Indeed, I fear for you the punishment of a terrible day."