Sura al-Isrāʾ 17:59

وَمَا مَنَعَنَآ أَن نُّرْسِلَ بِٱلْأَيَٰتِ إِلَّآ أَن كَذَّبَ بِهَا ٱلْأَوَّلُونَ وَءَاتَيْنَا ثَمُودَ ٱلنَّاقَةَ مُبْصِرَةً فَظَلَمُوا۟ بِهَا وَمَا نُرْسِلُ بِٱلْأَيَٰتِ إِلَّا تَخْوِيفًا

wa-mā manaʿanā an nnursila bil-ayāti illā an kadhdhaba bihā l-awwalūna wa-ātaynā thamūda l-nāqata mubṣiratan fa-ẓalamū bihā wa-mā nursilu bil-ayāti illā takhwīfan

And We refrain from sending the signs, only because the men of former generations treated them as false: We sent the she-camel to the Thamud to open their eyes, but they treated her wrongfully: We only send the Signs by way of terror (and warning from evil).