There is a concept among Most traditional Jews of ressurection of the dead. This is said to occur when the Messiah comes.
Not all Jews take this belief literally.
The Sadducee's were the Jewish sect that denied any kind of resurrection of the body. They also denied any kind of spirit realm.
The first Christians were Jews and were accustomed to Jewish scriptures which became Christian scripture as well.
The Sadducees, a Jewish religious group during the time of Jesus, did not believe in a bodily resurrection. They only accepted the authority of the Torah (the first five books of the Hebrew Bible) and did not believe in an afterlife or resurrection of the dead.
Jesus had a tense and adversarial relationship with the Sadducees. They were a group of Jewish religious leaders who denied the concept of the afterlife and the resurrection. This brought them into conflict with Jesus, who taught about the resurrection and challenged their authority.
Jesus observed Passover, as he was Jewish. Easter did not exist then. It was his resurrection that created Easter.
Matthew 22:23 - The same day the Sadducees, who say there is no resurrection, came to Him and asked Him,[NKJV]
In Western Christianity, the annual day that the resurrection of JESUS is observed is on the Sunday immediately following the Jewish Paschal Full Moon (meaning Passover) date of the year.
The Pharisees were a Jewish sect known for their strict adherence to the Torah and oral traditions, believing in the resurrection of the dead and the existence of angels and spirits. The Sadducees were another Jewish sect that rejected the oral tradition, denying the resurrection of the dead and the existence of angels. The Essenes were a group of Jewish ascetics who lived in communal settlements, practiced celibacy, and focused on ritual purity.
Jesus of Nazareth was raised in a Jewish home. Christianity was not formed until after Jesus' death and His resurrection.
The festival of Easter is the Christian church's marking of the death and resurrection of Jesus Christ, which occurred at the time of the Jewish festival of Passover.
The coming of Christ is foretold in the Jewish Torah (the old testament). The new testament documents the birth of Christ, his ministry, death and resurrection as predicted in the Torah.
Jesus was not committed to Christianity because He was Jewish. Christianity did not begin until after Jesus died.