Deuteronomy

The name means 'second law' — it's Moses restating and expanding God's commands to the new generation about to enter Canaan. It contains the Shema (6:4), the blessings and curses (chapters 28-30), and Moses' final blessing and death. Jesus quoted Deuteronomy more than almost any other book when resisting Satan's temptation in the wilderness. It's the theological heart of the OT.