Islam believes in 'Tawheed' which is not merely monotheism i.e. belief in one God, but much more. Tawheed literally means 'unification' i.e. 'asserting oneness' and is derived from the Arabic verb 'Wahhada' which means to unite, unify or consolidate.
Tawheed can be divided into three categories.
Tawheed ar-Ruboobeeyah (maintaining the unity of Lordship):
The first category is 'Tawheed ar-Ruboobeeyah'. 'Ruboobeeyah' is derived from the root verb "Rabb" meaning Lord, Sustainer and Cherisher.
Therefore 'Tawheed-ar-Ruboobeeyah' means maintaining the unity of Lordship. This category is based on the fundamental concept that Allah (swt) alone caused all things to exist when there was nothing. He created or originated all that exists out of nothing. He alone is the sole Creator, Cherisher, and Sustainer of the complete universe and all between it, without any need from it or for it.
Tawheed al-Asmaa was-Sifaat (maintaining the unity of Allah's name and attributes):
The second category is 'Tawheed al Asmaa was Sifaat' which means maintaining the unity of Allah's name and attributes. This category is divided into five aspects:
Allah should be referred to as described by Him and His Prophet
Allah must be referred to according to the manner in which He and His prophet have described Him without explaining His names and attributes by giving them meanings other than their obvious meanings.
Allah must be referred to as He has referred to Himself
Allah must be referred to without giving Him any new names or attributes. For example Allah may not be given the name Al-Ghaadib (the Angry One), despite the fact that He has said that He gets angry, because neither Allah nor His messenger have used this name.
Allah is referred to without giving Him the attributes of His creation
In a reference to God, we should strictly abstain from giving Him the attributes of those whom He has created. For instance in the Bible, God is portrayed as repenting for His bad thoughts in the same way as humans do when they realise their errors. This is completely against the principle of Tawheed. God does not commit any mistakes or errors and therefore never needs to repent.
The key principle when dealing with Allah's attributes is given in the Qur'an in Surah Ash-Shur
"There is nothing whatever like unto Him, And He is the One that hears and sees (all things)."
Hearing and seeing are human faculties. However, when attributed to the Divine Being they are without comparison, in their perfection, unlike when associated with humans who require ears, eyes, etc. and who are limited in their sight and hearing in terms of space, time, capacity, etc.
God's creation should not be given any of His attributes
To refer to a human with the attribute of God is also against the principle of Tawheed. For example, referring to a person as one who has no beginning or end (eternal).
Allah's name cannot be given to His creatures
Some Divine names in the indefinite form, like 'Raoof' or 'Raheem' are permissible names for men as Allah has used them for Prophets; but 'Ar-Raoof' (the Most Pious) and Ar-Raheem (the most Merciful) can only be used if prefixed by 'Abd' meaning 'slave of' or 'servant of' i.e. 'Abdur-Raoof' or 'Abdur-Raheem'. Similarly 'Abdur-Rasool' (slave of the Messenger) or 'Abdun-Nabee' (slave of the Prophet) are forbidden.
Tawheed al-Ibaadah (maintaining the unity of worship):
Definition and meaning of 'Ibadaah':
'Tawheed al-Ibaadah' means maintaining the unity of worship or 'Ibaadah'. Ibaadah is derived from Arabic word 'Abd' meaning slave or servant. Thus Ibaadah means servitude and worship.
All three categories to be followed simultaneously.
Only believing in the first two categories of Tawheed without implementing Tawheed-al-Ibaadah is useless. The Qur'an gives the examples of 'Mushrikeens' (idolaters) of the Prophet's time who confirmed the first two aspects of Tawheed. It is mentioned in the Qur'an:
Say: 'Who is it that sustains you (in life) from the sky and from the earth? Or who is it that has power over hearing and sight? And who is it that brings out the living from the dead and the dead from the living? And who is it that rules and regulates all affairs?' They will soon say, 'Allah'. Say, 'Will you not then show piety (to Him)?'
A similar example is repeated in Surah Zukhruf of the Glorious Qur'an:
If thou ask them, Who created them, they will certainly say, 'Allah': how then are they deluded away (from the Truth)?
The pagan Meccans knew that Allah (swt) was their Creator, Sustainer, Lord and Master. Yet they were not Muslims because they also worshipped other gods besides Allah. Allah (swt) categorised them as 'Kuffaar' (disbelievers) and 'Mushrikeen' (idol worshippers and those who associate partners with God).
And most of them believe not in Allah without associating (others as partners) with Him!"
Thus 'Tawheed al-Ibaadah' i.e. maintaining the unity of worship is the most important aspect of Tawheed. Allah (swt) alone deserves worship and He alone can grant benefit to man for his worship.
Definition: The omission of any of the above mentioned categories of tawheed or deficiency in the fulfillment of any criteria of Tawheed is referred to as 'shirk'.(Please note that the Arabic word 'Shirk' has the same sound as in the English word 'ship' and not as in the English word 'shirk' which means 'to evade'
'Shirk' literally means sharing or associating partners. In Islamic terms it means associating partners with Allah and is equivalent to idolatry.
Shirk is the greatest sin that Allah will never forgive:
The Qur'an describes the greatest sin in Surah Al-Nisa':
Allah forgives not that partners should be set up with Him; but He forgives anything else, to whom He pleases; to set up partners with Allah is to devise a sin most heinous indeed.
The same message is repeated in Surah Al-Nisa':
Allah forgives not (the sin of) joining other gods with Him; but He forgives whom He pleases other sins than this: one who joins other gods with Allah, has strayed far, far away (From the Right).
Shirk leads to hell fire:
The Qur'an says in Surah Ma'idah:
They do blaspheme who say: 'Allah is Christ the son of Mary.' But said Christ: 'O Children of Israel! Worship Allah, my Lord and your Lord'. Whoever joins other gods with Allah - Allah will forbid him the Garden, and the Fire will be his abode. There will for the wrongdoers be no one to help.
Worship and Obedience to none but Allah:
The Qur'an mentions in Surah Ali-'Imran:
Say: "O people of the Book! Come To common terms as between us and you: That we worship none but Allah; That we associate no partners with Him; That we erect not, from among ourselves, lords and patrons other than Allah." If then they turn back, say ye: "Bear witness that we (at least) are Muslims (bowing to Allah's Will)."
The Glorious Qur'an says:
"And if all the trees on earth were pens and the Ocean (were ink), with seven Oceans behind it to add to its (supply), yet would not the Words of Allah be exhausted (In the writing): for Allah is Exalted in power, Full of Wisdom."
Our analysis of Concept of God in various Religion shows that monotheism is an integral part of every major religion of the world. However, it is unfortunate that some adherents of these religions violate the teachings of their own scriptures and have set up partners to Almighty God.
An analysis of the scriptures of various religions, reveals that all scriptures exhort mankind to believe in, and submit to One God. All these scriptures condemn the association of partners to God, or the worship of God in the form of images. The Glorious Qur'an says:
O men! Here is a parable set forth! Listen to it! Those on whom, besides Allah, you call, cannot create (even) a fly, if they all met together for the purpose! And if the fly should snatch away anything from them, they would have no power to release it from the fly. Feeble are those who petition and those whom they petition!