The Zoroastrian religion is commonly thought to be the forerunner of the Abrahamic religions. This website calls Zoroastrianism "A Universal Religion: Good Thoughts, Good Words, Good Deeds," and says "Who fears God, does not know God." Links lead to related off-site articles on topics such as philosophy and historical background. Zoroastrianism is thought to be the world's first monotheistic religion. Monotheism is the belief that there is only one god as opposed to polytheism which holds that there are many gods.

The Abrahamic religions are: Judaism, Christianity, and Islam. Judaism is thought to come through Abraham's son Isaac, grandfather of Judah, as described in the Old Testament of the Bible. Christianity is the spiritual descendant of Isaac as described in the Gospels of the New Testament of the Christian Bible. Islam, whose adherents are called Muslims, is thought to come through Abraham's son Ishmael. Zoroastrianism is thought to precede all of these religions.

It is believed by scholars that the oldest of the Abrahamic religions, Judaism, borrowed its central tenets, esp. monotheism, directly from Zoroastrianism when the Jews were captives in Babylon (see wikipedia article).