All,
1. How do you know what "ancient Judaism believed" in the absence of written documents? Psychic powers? I have the Tanach and Talmud, and they both teach afterlife, eternity, eternal judgment, etc. as well as the triunity of God. You cannot sing "Tradition!" and confidently assert pre-Bible Jewish thought unless you have other documents I've never heard of, nor have you heard of!
2. I could do little better than to point to Exodus 3 to explain the reality of the afterlife in the Tanach.
Thanks.