Allah, the All Wise, All Knowing, All Merciful and Just, created this Universe in order to test and examine His obedient slaves and reward them, and to punish the disobedient. He Says (what means): "We did not create the heavens and the earth and that between them in play. We did not create them except in truth, but most of them do not know." [Quran 44: 38-39]

　　Allah also made clear the main goal for the creation of mankind, Saying (what means): "I did not create the Jinn and Mankind except for My worship" [Quran 51: 56]

　　Allah, the Exalted, did not leave His slaves to rely upon their intellect and inclination to guide them to the correct way; rather He sent them Messengers as bringers of good tidings and warners. He sent the revealed Books with them to be a reference in those matters wherein they disagreed, so that no excuse would remain for the people and the proof would be established against them. Thus, after sending the Messengers, there would be no further excuse for people before Allah.

　　Indeed, their mission covered every good and banished every evil. They brought to humankind everything needed for their well being and happiness in this world and the Hereafter. There is nothing good, which they did not inform the people about and nothing evil that they did not warn the people against.

　　‘Abdullaah bin `Amr bin Al-`Aas, may Allah be pleased with him, said that the Prophet said: "There was never a Prophet before me except that it was a duty upon him that he should guide his nation to every good that he knew and warn them against every evil that he knew…" [Muslim]

　　Indeed, calling to Allah was the mission of the Messengers in order to bring the people out from darkness into light. There are many basic principles upon which their calls were based, which were the starting point for calling to Allah. These fundamental principles are:

　　1. Tawheed (Monotheism)

　　2. Prophethood

　　3. The Hereafter

　　Every book revealed by Allah gave great importance to these points. The most important and sublime of these three principles and the most fundamental of them all is Tawheed (Oneness) of Allah.

　　Allah Says (which means): "And We certainly sent into every nation a Messenger, (saying): 'Worship Allah and avoid Taaghoot (false objects of worship).' " [Quran 16: 36]

　　Allah has informed us about some of the Prophets, may Allah exalt their mention, and how they faced their people. We see that all of them proceeded upon the universal way laid down by Allah and followed the methodology Allah established for all of them. Not a single one of them is at variance with it, Allah Says (which means): "And We had certainly sent Nooh to his people, (saying): 'Indeed, I am to you a clear warner, that you not worship except Allah. Indeed, I fear for you the punishment of a painful Day.'" [Quran 11: 25-26]

　　The noblest of all Prophets and the last of them, Muhammad bin ‘Abdullaah (who was sent with the greatest, most complete and comprehensive message), began with what all the Prophets, may Allah exalt their mention, started their Da’wah (call) -- calling to the 'Aqeedah (creed) of Tawheed (Oneness of Allah), and calling for all worship to be made purely and sincerely for Allah alone. Allah's Messenger started with the principle: 'Witness that none has the right to be worshipped except Allah.'

　　Allah Says (what means): "Say, (O Muhammad): 'O mankind, indeed I am the Messenger of Allah to you all, (from him) to Whom belongs the dominion of the heavens and the earth. There is no deity except Him; He gives life and causes death.' So believe in Allah and His Messenger, the unlettered Prophet, who believes in Allah and His words, and follow him that you may be guided." [Quran 7: 158]

　　The verses in this regard are many, what we quote here is just one example. With regard to the Sunnah (traditions and approved actions of Prophet Muhammad ), there are many clear indications that Allah's Messenger began his call to Islam with Tawheed.

　　1.