In conversation with the Saducees, who believe in God, but not in a life after death, Jesus points out that God is God of the living. It makes no sense to be God of the dead. Jesus also points out to His hearers that life beyond the grave is different from life in this world. We will be children of the resurrection.
This understanding of life and death, and what lies beyond, was demonstrated in the time of the Maccabees, in the story of the seven sons put to death for their religion. Each son expresses a belief in the justice of God, the reward of a good life and the punishment of sinners. All the injustices of this world will be addressed and redressed. Where people have been robbed of life in this world, and deprived of its hopes and joys, there will be a restoration and a fulfilment of life for them in heaven.