﴿ وَإِن يُكَذِّبُوكَ فَقَدْ كَذَّبَتْ قَبْلَهُمْ قَوْمُ نُوحٍۢ وَعَادٌۭ وَثَمُودُ ﴾

“AND IF THEY [who are bent on denying the truth] give thee the lie, [O Muhammad, remember that, long] before their time, the people of Noah and [the tribes of] Ad and Thamud gave the lie [to their prophets],”

And if they deny you — these words to the end of the statement are meant to comfort the Prophet s — the people of Noah denied before them kadhdhabat in the feminine person on the basis of the overall import and ‘Ād the people of Hūd and Thamūd the people of Sālih