To the worshipers of heavenly bodies it relates as a reminder the story of Abraham:
“When night outspread over him he saw a star and said, ‘This is my Lord.’ But when it set he said, ‘l love not the setters.’ When he saw the moon rising, he said, ‘This is my Lord.’ But when it set he said, ‘If my Lord does not guide me I shall surely be of the people gone astray.’ when he saw the sun rising, he said, ‘This is my Lord; this is greater!’ But when it set he said, ‘O my people, surely I am quit of what you associate with God. I have turned my face to Him who originated the heavens and the earth, a man of pure faith; I am not of the idolaters.’” [Surah Al-An’am, 6: 76-79]

And when, later on, the Prophet comes into contact with the Jews and Christians, the Qur’an condemns their belief in the divine nature of human-beings.

“The Jews say, ‘Ezra is the son of God.’ The Christians say, ‘The Messiah is the son of God.’ That is the utterance of their mouths, conforming with the unbelievers before them. God assail them! How they are perverted.” [Surah At-Tawbah, 9: 30]
It tells them that if everything is created by God then it must be His servant and cannot, therefore be his son, [Surah Maryam, 19: 88-95].
It then goes on to explain to the Christians the real nature of Jesus.
“Truly, the likeness of Jesus in God’s sight is as Adam’s likeness; He created him of dust, then said He unto him ‘Be!’ and he was.” [Surah Aal-`Imran, 3: 59]
For someone to take something as a god, it is not necessary that he should acknowledge it as such or worship it in a ritualistic way; it is enough for him to follow its dictates obediently, or devote to it acts or have towards it feelings which should be devoted to or felt towards God only. There are many such unacknowledged gods.
“Hast thou seen him who has taken his caprice to be his God? Wilt thou be a guardian over him?” [Surah Al-Furqan, 25: 43]

“They have taken their rabbis and their monks as lords apart from God, and the Messiah, Mary’s son, and they were commanded to serve but one God.” [Surah At-Tawbah, 9: 31]
Thus to be a Muslim – i.e. to surrender oneself to God – it is necessary to believe in the unity of God in the sense of His being the only creator, preserver and nourisher. But this belief – later on called tawhid ar-rububiyya – is not enough. In fact many of the idolaters did know and believe that it is the supreme God alone who can do all this. But that was not enough to make them Muslims. To tawhid ar-rububiyya one must add tawhid al-uluhiyya i.e. one must acknowledge the fact that it is this God alone who deserves to be worshiped, and therefore abstain from directing any of one’s acts of worship to someone or something else. In the Qur’an the argument for tawhid al-uluhiyya is based on tawhid ar-rububiyya i.e. if it is God alone who creates and controls everything why then and to what end do you worship others beside Him?

“O you men, serve your Lord who created you, and those that were before you; haply so you will be god-fearing; who assigned to you the earth for a couch, and heaven for an edifice, and sent down out of heaven water, wherewith He brought forth fruits for your provision; so set not up rivals to God wittingly.” [Surah al-Baqarah, 2: 21-22]
Having known the true God, man is called upon to affirm what he knows i.e. to believe and have faith in God, and not allow any ulterior motives to induce him to deny a fact which he knows to be true.

“… that they who have been given knowledge may know it is the truth from thy Lord and so believe in it, and thus their hearts become humble unto him.” [Surah Al-Hajj, 22: 54]

“But when our signs came to them visibly, they said, “This is a manifest sorcery;’ end they denied them, though their souls acknowledged them, wrongfully and out of pride.” [Surah An-Naml, 27: 14]
When faith enters a person’s heart, it causes therein certain mental states, which result in certain apparent actions, both of which are the proof of true faith.
Foremost among those mental states is the feeling of gratitude towards God, which could be said to be the essence of ibadah (worshiping or serving God).
This feeling of gratitude is so important that a nonbeliever is called kafir which means, ‘one who denies a truth’ and also ‘one who is ungrateful.’ One can understand why this is so when one reads in the Qur’an that the main motive for denying the existence of God is that of unjustified pride. Such a proud person feels that it does not become him to be created or governed by a being whom he must thus acknowledge to be greater than himself and to whom he must be grateful.

“Those who dispute concerning the signs of God without any authority come to them, in their hearts is only pride that they shall never attain.” [Surah Ghafir, 40: 56]
With the feeling of gratitude goes that of love.

“There are some people who take to themselves (for worship) others apart from God loving them as they should love God: But those who believe, love God more ardently than they love anything else.” [Surah Al-Baqarah, 2: 165]
A believer loves and is grateful to God for His bounties, but being aware of the fact that his good deeds, whether mental or physical, are far from being commensurate with Divine favors, he is always anxious lest because of his sins God should withhold from him some of these favors or punish him in the hereafter. He therefore fears Him, surrenders himself to Him, and serves Him with great humility.
“Your God is one God, so to Him surrender. And give thou good tidings unto the humble who, when God is mentioned, their hearts quake.” [Surah Al-Anfal, 8: 2]

One cannot be in such a mental state, without being almost all the time mindful of God. Remembering God is thus the life-force of faith, without which it fades and might even wither away.

So: “The faithful are those who remember God, standing and sitting, and on their sides.”[Surah Aal-`Imran, 3: 191]

The Qur’an therefore prescribes and describes, in great detail ways and means of helping man to remember God and keep his faith alive. All Qur’anic and Prophetic injunctions and prohibitions which extend to all aspects of human life acts of worship and personal matters, social relations, political order, etc., etc. – are designed to put man in a state which is conducive to God’s remembrance. The details of this Islamic way of life were expounded in the Madina period, and we shall not therefore be concerned with them now. But the main principles of this new order were already laid down in the Makkan period, and will be summarized at the end of this chapter.

We shall now go on to deal with the other pillars of faith. These are belief in life after death, in God’s angels, His books, His messengers and His qadar, the arguments for all of which are almost entirely based on the assumption that the audience believes in God.