Jewish belief begins with the existence of a single God, unitary in nature and utterly distinct from humanity, who created and holds power over all things. It further asserts a special covenant between God and the Jewish people beginning with Abraham, in which Jews are called to be a “light to the nations.” Moses is considered the chief of all the prophets, and his Torah—the first five books of the Hebrew scriptures—is believed to be God's revelation. Specific theological beliefs vary widely within Judaism. As a rule, Jews believe in free will and divine reward and punishment, but the afterlife is a much less prominent theme than in Christianity and Islam. Practice is critical: a relationship with God through obedience to the divine law, however differently understood. Belief in a coming messiah varies, ranging from the Orthodox expectation of a king from the House of David who will rule the Jewish people according to Jewish law to the Reform rejection of the idea of a messiah altogether.