Resurrection. Basically...
He began with a concept about resurrection which has existed before especially in Hellenistic belief, thus he tries to spread the idea that God finally conceded to the ways of Hellenistic worshipping and hence adopting the falsehood of the past and blessed it and permits it so that mankind will just worship a new version of God in human form.
Also Greek Christians, the ones that spread the Pauline version about the life Messiah in 26/27 Greek books centres around the resurrection theme. While Nasoreans that adhere to companions of Jesus Messiah did not believe in resurrection of the Messiah.
All of the Quran verses that he quoted, simply talks about death and resurrection for judgement from God. No verse about Jesus having death on earth followed by resurrection on earth; as a decree to mankind that the Hellenistic style of a human-God dying and resurrecting shall then be accepted as the new 'truth' despite being false in the past.
In Islam, if Jesus Messiah has experienced death then there will be no event of descending from sky to fight false Messiah to only experience a second death and later second resurrection. And so, if Jesus Messiah is still alive, then he will be descending down to fight false Messiah and later experience his death and resurrection.
