Overall meaning : Allah says to His Prophet, Muhammad, may Allah bless him and grant him peace: If Allah afflicts you with any type of harm, none can remove it but He; and if He blesses you with anything good, know that He has power over all things, and no one can withhold His bounty.
The Almighty then points out His immense power and might and total authority, stating that everything and everyone is under His absolute control, that He reigns supreme over His creation and is high above them in His being, power and authority, and that He is the All-Wise, the All-Aware.
Then He directs His Prophet, Muhammad, may Allah bless him and grant him peace, to ask those who reject the truth: Who is the greatest witness to bear testimony to the truthfulness of my message? He also orders him to provide the answer, saying, 'It is Allah, who does not lie, make a mistake or omit anything in His testimony. He is witness between me and you. He has revealed to me this Qur’an so that I may thereby warn you and whomsoever it reaches of His punishment.’ Then He instructs him to ask such deniers of the truth if they really testify that there are other gods besides Allah. If they say they do, He directs him to say to them that he will never bear such witness and to affirm that there is no other god deserving of worship except one God—Allah—and that he utterly disowns whatever they worship besides Him.