Surah Yunus, Verse 38

أَمۡ يَقُولُونَ ٱفۡتَرَىٰهُۖ قُلۡ فَأۡتُواْ بِسُورَةٖ مِّثۡلِهِۦ وَٱدۡعُواْ مَنِ ٱسۡتَطَعۡتُم مِّن دُونِ ٱللَّهِ إِن كُنتُمۡ صَٰدِقِينَ٣٨

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

Or do they say [about the Prophet (ﷺ)], "He invented it?" Say, "Then bring forth a sūrah like it and call upon [for assistance] whomever you can besides Allāh, if you should be truthful."