Immortality teas unknown to the Jews, and was rejected by the Sadducees because it was not in the Pentateuch.

The immortality of the soul was well known to the Jews. The Sadducees were a small minority who were remarkable among the Jews precisely because they denied it. The majority of the Jews, therefore, held it. They were well aware of the apparition of the soul of Samuel to Saul in I. Sam. (Kgs.), XXVIIL, 15. Our Lord quoted the Pentateuch against the Sadducees, proving immortality from Exod. III., 6. “I am the God of Abraham, and the God of Isaac, and the God of Jacob.” And He said, “He is not the God of the dead, but of the living.” In other words, He is, not was, their God.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty