Quran 29:50 from Surah Al-Ankaboot on Divine Marvels.
وَقَالُواْ لَوۡلَآ أُنزِلَ عَلَيۡهِ ءَايَٰتٞ مِّن رَّبِّهِۦۚ قُلۡ إِنَّمَا ٱلۡأٓيَٰتُ عِندَ ٱللَّهِ وَإِنَّمَآ أَنَا۠ نَذِيرٞ مُّبِينٌ
English translation: And they say Why not are sent down to him (the) Signs from his Lord Say Only the Signs (are) with Allah and only I (am) a warner clear
Transliteration: waqalu lawla unzila alayhi ayatun min rabbihi qul innama al-ayatu inda al-lahi wa-innama ana nadhirun mubinun