Islam, that are, Unity and worship of God and service to humanity and/or all life on Earth. Noah, Moses and Muhammad are examples of Law-bearing Prophets. Non law-bearing Prophets/Messengers do not bring forth any new revelation but are followers of a previous revelation given by a Law-bearing Prophet. They are usually Successors (Arabic: Khulafa) of the previous Law-bearing Prophets in which they follow. Sometimes, they are not Successors of previous Prophets and are thus just contemporaries of Law-Bearing Prophets. The Prophets of the Old Testament (David, Solomon etc.) are examples of Successor-Prophets of Moses and follow his Mosaic Law. Hud, a Prophet mentioned exclusively in the Qur'an, is an example of a contemporary Law-bearing Prophet, who in this case is Noah. Religious evolution The Ahmadiyya Writings reveal that Prophets have always been sent by God in the past to all nations of the world, as part of the single religion from God, which is Islam. Religion is taught to be progressive and the Prophets reveal teachings either more advanced than their preceding religions or suited for each specific time, place and society. If one were to strip all religions of their innovative teachings, one would find that they are all essentially identical, according to Ahmadiyya belief. All religions, according to the Ahmadiyya teaching of the evolution of religion, were part of Islam and were revealed in parts like pieces of a jigsaw puzzle. But then, according to Ahmadiyya belief, God fully revealed the whole of Islam, in its perfect form, to Muhammad. Islam was thus called the 'Seal of the Religions' (Arabic: Khatam-ud-Din) just as Muhammad was called "Seal of the Prophets". One of the earliest recorded expressions of this religious perennialism is found in the Bhagavad-Gita, which the Ahmadiyya Community acknowledges as of Divine origin: "I come, and go, and come. When Righteousness declines, O Bharata! When Wickedness is strong, I rise, from age to age, and take visible shape, and move a man with men, succouring the good, thrusting the evil back, and setting Virtue on her seat again." (Bhagavad-Gita, Chapter IV) Prophets as celestial beings "We have adorned the lowest heaven with an adornment – the planets." (37:7) "And We have, indeed, made mansions of stars in the heaven and have adorned it for beholders." (15:17) "Blessed is He Who has made in the heaven mansions of the stars and has placed therein a Lamp producing light