﴿ ۞ وَٱذْكُرْ أَخَا عَادٍ إِذْ أَنذَرَ قَوْمَهُۥ بِٱلْأَحْقَافِ وَقَدْ خَلَتِ ٱلنُّذُرُ مِنۢ بَيْنِ يَدَيْهِ وَمِنْ خَلْفِهِۦٓ أَلَّا تَعْبُدُوٓا۟ إِلَّا ٱللَّهَ إِنِّىٓ أَخَافُ عَلَيْكُمْ عَذَابَ يَوْمٍ عَظِيمٍۢ ﴾

“AND REMEMBER that brother of [the tribe of] Ad, how - seeing that [other] warnings had already come and gone within his own knowledge as well as in times beyond his ken - he warned his people [who lived] among those sand-dunes: “Worship none but God! Verily, I fear lest suffering befall you on an awesome day!””

And mention the brother of ‘Ād namely Hūd peace be upon him when idh … from here to the end of the verse constitutes an inclusive substitution he warned his people he threatened them at Ahqāf ‘the Sand dunes’ is the name of a valley in Yemen where their dwellings were located — and already warners messengers had passed away before him and after him that is to say before Hūd came to them and after him to their peoples — saying ‘Do not worship anyone but God the statement beginning with wa-qad khalat ‘and already warners had passed away’ is a parenthetical one. Truly I fear for you — should you worship other than God — the chastisement of a dreadful day’.