Quran 2:23 from Surah Al-Baqara on Divine Marvels.
وَإِن كُنتُمۡ فِي رَيۡبٖ مِّمَّا نَزَّلۡنَا عَلَىٰ عَبۡدِنَا فَأۡتُواْ بِسُورَةٖ مِّن مِّثۡلِهِۦ وَٱدۡعُواْ شُهَدَآءَكُم مِّن دُونِ ٱللَّهِ إِن كُنتُمۡ صَٰدِقِينَ
English translation: And if you are in doubt about what We have revealed to Our slave then produce a chapter [of] like it and call your witnesses from other than Allah if you are truthful
Transliteration: wa-in kuntum fi raybin mimma nazzalna ala abdina fatu bisuratin min mith'lihi wa-id'u shuhadaakum min duni al-lahi in kuntum sadiqina