'And when it is recited' means from any reciter it may be. 'The Qur'an' refers to that which encompasses all that benefits them in their worldly life and their Hereafter. It distinguishes between everything that is ambiguous, between the forbidden and the lawful, and other than that. 'They do not prostrate' means they do not submit with their hearts and do not humble themselves to the truth by the linguistic prostration. They do not perform the legal prostration for its recitation because it is the master of speech. It has revealed knowledge that cannot be counted, along with the testimony of itself through its miraculous nature that it is from Allah. They have no excuse in that except ignorance or inability. There is no ignorance with the Qur'an, nor is there inability with strength and choice.