Shared ground
Mark presents this exchange as a public test of Jesus in Jerusalem. The Sadducees, who deny resurrection, build an extreme marriage scenario from Moses’ marriage-duty rule and ask whose the woman will be “when they rise” (Mark 12:18–23).
Jesus answers by correcting the assumption underneath the riddle. Resurrection life is not simply a restart of current social arrangements: “when they rise from the dead, they neither marry nor are given in marriage” (Mark 12:24–25). The comparison to angels functions to support that point within the argument.
Jesus then addresses the larger claim that resurrection is impossible by pointing to the burning bush passage in Moses, where God says, “I am the God of Abraham…Isaac…Jacob,” and concludes that God “is not God of the dead, but of the living” (Mark 12:26–27). Whatever steps readers supply between the quote and the conclusion, Mark’s portrayal is clear: Jesus treats the Sadducees’ denial as a serious mistake about both Scripture and God’s power, and he frames the living God as one whose relationship to his people is not nullified by death.