Why is heaven not taught in the Old Testament?
Israel was an earthly people with earthly promises, so the Old Testament does not present heaven as the Jew's hope. In the age of grace, believers are a heavenly people with heavenly promises, and their citizenship is in heaven, though they live on earth.
Les explains that the question came up years ago: why isn't heaven taught in the Old Testament, and why did the Jew have no concept of dying and going to heaven? His answer was that Israel was an earthly people with earthly promises. By contrast, we in the age of grace are a heavenly people with heavenly promises. Even though we are on the earth, our citizenship is in heaven. We are already a heavenly people by the power of God. This fits the context of being translated from darkness into the kingdom of His dear Son.