After answering the Sadducees’ question about marriage, Jesus turned to the larger question of the resurrection (rising from the dead).
Even Moses demonstrates that: Jesus used the books of Moses to show that the resurrection is true. These books (Genesis, Exodus, Leviticus, Numbers, and Deuteronomy) were the only Scripture the Sadducees recognized as authoritative.
the God of Abraham … Jacob: God called himself the God of Abraham, Isaac, and Jacob long after these patriarchs had died. Since he was still their God, they must have had a continuing existence after death.