Charles Ellicott Commentary Matthew 22:31

"But as touching the resurrection of the dead, have ye not read that which was spoken unto you by God, saying," — Matthew 22:31 (ASV)

That which was spoken to you by God—In St. Mark and St. Luke, we find the addition “at the bush,” with the words probably being a reference to the section of the Law containing Exodus 3 and known by that title. It should be noted that there are many other passages scattered throughout the Old Testament (such as Job 19:25–26, Psalms 16:10–11, and Daniel 12:2) where the hope of immortality, and even of a resurrection, is expressed more clearly. However, our Lord meets the Sadducees on their own ground and quotes from the Law, which they recognized as having supreme authority.

The principle implied in the reasoning is that the union of the divine Name with a person's name, as in I am the God of Abraham, involved a relationship that existed not only in the past but was still present when the words were spoken. This meant something more than simply, “I am the God whom Abraham worshiped in the past.” If the relationship was a permanent one, then it followed that those whose names were joined with the name of God in this way were living and not dead.