Alif-Lam-Mim. [These letters are one of the miracles of the Quran, and none but Allah (Alone) knows their meanings.]
The revelation of the Book (this Quran) is from the Lord of the ‘Alamin (mankind, jinns and all that exists) in which there is no doubt!
Or do they say, “He invented it”? Rather, it is the truth from your Lord, [O Muhammad SAW], that you may warn a people to whom no warner has come before you [so] perhaps they will be guided.
Chapter 32 As-Sajdah : Verses 1-3
The Qur’an is the Book of Allah in which there is no Doubt
(The revelation of the Book in which there is no doubt,) means, there is no doubt whatsoever that it has been revealed
(from the Lord of all that exists.) Then Allah tells us about the idolators:
(Or say they: “He has fabricated it”): they say, he has fabricated it, i.e., he has made it up by himself.
(Nay, it is the truth from your Lord, so that you may warn a people to whom no warner has come before you, in order that they may be guided.) means, in order that they may follow the truth.