A. Yusuf Ali:Translation:
Say: "If the whole of mankind and Jinns 2288 were
to gather together to produce the like of this Qur´an,
they could not produce the like thereof, even if they
backed up each other with help and support. 2289

Muhammad Asad:Translation:
Say: "If all mankind and all invisible beings 103 would come together with a view to producing the like of this Qur'an, they could not produce its like even though they were to exert all their strength in aiding one another!"
2288 For the meaning of "Jinns", see n. 929 to 6:100.
2289 The proof of the Qur'an is in its own beauty and nature, and the circumstances in which it was promulgated. The world is challenged to produce a Book like it and has not produced one. It is the only revealed Book whose text stands pure and uncorrupted today. Cf., for a similar challenge, 2:23,10:38, and 11:13.