وَاِنۡ كُنۡتُمۡ فِيۡ رَيۡبٍ مِّمَّا نَزَّلۡنَا عَلٰي عَبۡدِنَا فَاۡتُوۡا بِسُوۡرَةٍ مِّنۡ مِّثۡلِهٖࣕ وَادۡعُوۡا شُهَدَآءَكُمۡ مِّنۡ دُوۡنِ اللّٰهِ اِنۡ كُنۡتُمۡ صٰدِقِيۡنَ

And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful