And if you are in doubt about what We have sent down [i.e., the Qur’ān] upon Our Servant [i.e., Prophet Muḥammad (ﷺ)], then produce a sūrah the like thereof and call upon your witnesses [i.e., supporters] other than Allāh, if you should be truthful.
Allah challenges those who have any doubt about the Qur’ān revealed to His servant, Muhammad (peace be upon him), to produce a chapter just like it, and to call their helpers, if they are truthful about what they say.