Surah Hud, Verse 13

أَمۡ يَقُولُونَ ٱفۡتَرَىٰهُۖ قُلۡ فَأۡتُواْ بِعَشۡرِ سُوَرٖ مِّثۡلِهِۦ مُفۡتَرَيَٰتٖ وَٱدۡعُواْ مَنِ ٱسۡتَطَعۡتُم مِّن دُونِ ٱللَّهِ إِن كُنتُمۡ صَٰدِقِينَ١٣

am yaqūlūna if'tarāhu qul fatū biʿashri suwarin mith'lihi muf'tarayātin wa-id'ʿū mani is'taṭaʿtum min dūni l-lahi in kuntum ṣādiqīna

Or do they say, "He invented it"? Say, "Then bring ten sūrahs like it that have been invented and call upon [for assistance] whomever you can besides Allāh, if you should be truthful."