Overall meaning :
down to His Servant and Messenger Muhammad, may Allah bless him and grant him peace, the Qur’an without there being in it any form of deviation whatsoever from the truth. He has sent it down unerringly straight without any consistencies, serving people’s interests, confirming the truth of all the divinely revealed books before it and having final authority over them, in order to warn with it the unbelievers of His severe punishment and to give the believers who do righteous deeds the good news that they will receive an excellent reward, namely Paradise, in which they will abide for ever; and also to warn with it the unbelievers who say, ‘Allah has offspring.’ They have no knowledge of such a false claim, neither they nor their ignorant forefathers.
Allah sternly criticises them for uttering such an enormity without real knowledge, saying: Dreadful indeed is this saying that issues from their mouths. They utter nothing but falsehood.
Then, comforting His Messenger, may Allah bless him and grant him peace, following the grief he experienced as a result of the disbelievers’ turning away from the true religion, He says: Do not destroy yourself with grief, Muhammad, if they turn away from you, do not believe in this Qur’an and stubbornly refuse to follow its teachings!