Jesus begins asking a question to show that people who have died will live again. He is scolding the Sadducees by asking this question. He is not looking for an answer.
This is the beginning of a question that end with the words "the God of Jacob" in verse 32. Jesus asks this question to remind the religious leaders of what they know from scripture. If this rhetorical question is translated as a statement, the question mark in verse 32 should become a period. Alternate translation: "you have read" (See: [[rc://en/ta/man/translate/figs-rquestion]])