Matthew 22:31

“But as touching the resurrection of the dead, have you not read what was spoken to you by God, saying,”

Having demonstrated the weakness of their argument Jesus then turned to what was ‘spoken by God'. Notice His emphasis on the fact that the Scriptures were ‘spoken by God'. Jesus constantly reveals His belief that the Scriptures reveal God's words and God's truth. But knowing their penchant for the Law He does not cite Isaiah 26:19 (or Daniel 12:2, although they may not have accepted Daniel as Scripture) for He knows that they will interpret such verses differently and will not accept their full force. He goes rather to the Law of Moses, and to a prominent saying regularly cited by all. He cites Exodus 3:6.

‘The resurrection of the dead' is a phrase found only here (but see Romans 1:4 where it is similar but anarthrous). Usually it is the resurrection from (ek) the dead. But John tells us that Jesus did teach the resurrection of all the dead, some to life and some to judgment (John 5:28).