Overall meaning : Allah, Glorified be He, clarifies the position of the People of the Book regarding Jesus, peace be upon him: The Jews and the Christians are at variance about Jesus, peace be upon him. Some of them, namely the Christians, assigned to him a divine nature; others, namely the Jews, showed no respect to him at all by charging him with being an illegitimate child—Far be it from him to be as such! Woe, then, to the unbleivers when they witness the dreadful and terrible Day of Resurrection. How clearly they will hear and see the truth on the Day of Judgement when they will come before Us! But the unbelievers who have wronged themselves by inventing lies about Allah are today in this world clearly far astray from the truth: They can neither hear it, nor see it nor understand it.
The Almighty then directs His Prophet Muhammad, may Allah bless him and grant him peace, to warn his idolatrous people of the horrors of the Day of Resurrection: Warn people, Muhammad, of the Day of Regret—Judgement Day when the wrongdoers will regret not having believed and done good deeds—when people will be judged and everything will be decided, for as yet they are today in this world heedless of what they have been warned of and they do not believe in Allah, nor in resurrection and recompense in the hereafter.
Then He points out what indicates His absolute power and supreme authority: We alone will remain after the earth and all those who dwell on it have perished, and to Us they will all be returned so that We will repay them according to their deeds.