Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. To proceed:
There is no contradiction whatsoever between these verses. Rather, they indicate that Jesus (peace be upon him) was neither killed nor crucified; Allah raised him to Himself, and he will die after his descent at the end of time.
Allah says through Jesus (peace be upon him):
“And peace be upon me the day I was born, the day I die, and the day I am raised alive.”
The commentators have explained that the verse speaks about the three stages through which a human being passes: his birth into this world, his death, and then his resurrection on the Day of Judgment.
Thus, his saying “the day I die” does not mean that Jesus (peace be upon him) had already died when the Qur’an was revealed. Rather, it means the day of his death in the future. Authentic hadiths indicate that he will descend at the end of time, kill the Antichrist (the Dajjal), and then die afterward.
Just as the statement “the day I am raised alive” does not mean that he had already been resurrected, likewise “the day I die” does not indicate that he died before his ascension.
Allah says:
“And there is none from the People of the Scripture except that he will surely believe in him before his death, and on the Day of Resurrection he will be a witness against them” [An-Nisa 4:159].
The commentators differed concerning the pronoun in “before his death”, with two interpretations:
First interpretation: The pronoun refers to Jesus (peace be upon him); meaning that all the People of the Scripture will believe in him when he descends at the end of time, before his death. This is the interpretation preferred by At-Tabari, Ibn Kathir, and others. It is supported by the hadith of Abu Hurayrah (may Allah be pleased with him) concerning the descent of Jesus (peace be upon him), after which he said: “Recite, if you wish...” and then recited this verse.
According to this interpretation, the verse is one of the indications of the descent of Jesus (peace be upon him) at the end of time, and that the People of the Scripture, when they see him and learn the truth about him, will believe in him.
Second interpretation: The pronoun refers to the individual from the People of the Scripture himself; meaning that every individual among the People of the Scripture will recognize the truth about Jesus (peace be upon him) at the time of death and believe in him when the truth becomes clear to him, but such belief at that moment will not benefit him.
Under either interpretation, the verse does not indicate that Jesus (peace be upon him) died before his ascension.
The stronger interpretation of the verse is that the People of the Scripture will believe in him when he descends, before his death. This agrees with the authentic hadiths establishing his descent at the end of time, his killing of the Dajjal, breaking the cross, killing the swine, and ruling according to the law of Islam.
The Qur’an does not establish that Jesus (peace be upon him) was killed or crucified. Rather, Allah says:
“They did not kill him, nor did they crucify him, but it was made to appear so to them,”
and He says: “Rather, Allah raised him to Himself” [An-Nisa 4:157–158].
Thus, he was raised alive, will descend at the end of time, then die, and be resurrected on the Day of Judgment. In this way, the apparent difficulties between the verses are resolved.
Anyone who discusses these matters with non-Muslims should speak with knowledge and clear evidence, relying on the Qur’an and authentic Sunnah, so that his call to the truth is based upon clear proof.
And Allah knows best.