Early songs like 'Blowin' in the Wind' derive central imagery from passages in the books of Ezekiel and Isaiah mid-career numbers like 'Forever Young' are infused with themes from the Bible, Jewish liturgy, and Kabbalah while late-period.
This apparently really is the real end of Rebirth for real this time. The Binding of Isaac: Repentance DLC is out now on Steam and the Epic Games Store and the huge expansion introduces a slew of new content like local co-op, additional playable characters, and fresh enemies.