The Belief in the Oneness of Allah (SWT) is central to Islam, & all other beliefs revolve around it [it]. However, it is not simply a matter of belief, but of firm conviction. Even though Allah (SWT) is hidden & invisible to the naked eye, He is clearly visible to positive reasoning and common sense. Wherever we look and explore, we find a unified system and an immaculate work of definite calculations and precise movements. Allah’s art of creation cannot be the work of more than one Lord, more than one Supreme Being. He has to be one; otherwise, there would bound to be a clash in the universal systems. There could not be natural symmetry, balance, and the existing fundamental similarities among creatures if there were more than one creator. Even human nature could have been divided and be concretely different in its most fundamental aspects, but since this is not the case, it shows that the Creator is one. If there were more than one god, various creatures, systems of life, and the very nature of humans would not only be very different, it would be impossible to coexist fro even a moment.
The more they try to disapprove His existence, the more they end up confirming it.
That is why all religions throughout human history, in one form or another, teach of one Supreme Being, one great God, even when some of them believe in lesser gods, and goddesses. Experience shows that even people who claim to believe in no god, deep down in their hearts, believe that this phenomenal universe must be the work of a Supreme Being.
Every field of science seems to accept that this universe and everything in it are a creation of some supreme and powerful being, and the results of their research point in this same direction, i.e., there is supreme being. Some, intentionally or unintentionally, in their attempt to disprove the existence of a supreme being, ironically end up proving its existence or at least fail to deny its existence concretely. The more they try to disprove His existence, the more they end up confirming it.
Humans are naturally connected to the Creator. Hence, no matter how much they have forgotten Him, they still call on him, especially when in need of help and when no else can help. They submit to Him whenever their power and intelligence fail and return to Him when there is no other place to go and no one else for whom to look or to whom to turn. This and many other experiences of daily life truly indicate that a mighty Lord exists and that He is one and cannot be more than one. Every divine revelation professes this unity, as do all of our natural faculties.
It is not just a matter of belief; it is a matter of fact that when we willfully and verbally declare the ‘Oneness of Allah’ (SWT) and recognise/ certify it by heart, we declare the truth and prepare to enter into Islam and return “home.” In Islam, tawhid (The Oneness of Allah SWT) is the centre of the Islamic belief system. The opposite of tawhid is Shirk. Shirk is not a forgivable sin,but it is forgiven only if Allah’s Oneness is embraced, along with the rest of Islam in its entirety. The heavenly guidance from Allah (SWT) that no one should commit shirk is clear, complete, and convincing, Thus, according to Islam, there is no other place for a mushrik (One who commits shirk), but eternal Hell.
The concept of tawhid is that Allah (SWT) is one and has no partners. Shirk is to associate an idol or human with Allah’s being and to relate someone or something with Allah as His partner, parent, son or daughter, to consider someone equal in power and in attributes or to believe someone has the personal power or ability to interfere or intercede in Allah’s will or in His work.
The main purpose of every prophet from Adam (A.S) to Prophet Muhammad (Peace be upon them), the Final Prophet, including but not limited to Nuh (Noah) (A.S), Ibrahim (Abraham) (A.S), Dawud (David) (A.S), Saleh (A.S), Musa (Moses) (A.S), and Isa (Jesus) (A.S), was to prevent their people from committing shirk (polytheism). They called upon their people to declare the tawhid (Oneness of Allah -SWT), to condemn shirk and to abandon the worship of anything else beside Allah (SWT). In light of the prophets’ sacrifices, hard work, proselytizing under adverse conditions, and teaching people about Allah (SWT) and His Oneness, every punishment from the Lord is justified for those who continued to commit shirk. Even today this is a matter for real concern and man must refrain from shirk, if he does not want to become the ultimate loser.
The clear, divine revelations about the Oneness of the Lord and those revelations denying the existence of any other god clearly conclude that none is worthy of worship besides Allah (S.W.T), the Omniscient and Omnipotent Lord. To worship anyone besides Allah (SWT) is another form of shirk. Muslims do not worship any prophet or associate prophets in Allah’s worship in any way, Although the prophets are all chosen men, some are closer to Allah (S.W.T) than others, and Prophet Muhammad (Peace be upon them) is the most beloved.
Prophets, angels, saints, and others are to be loved, honored, respected, and remembered, but not worshiped. Worship is due exclusively for Allah (SWT) .
Islam, as taught by the beloved Prophet Muhammad (Peace be upon them), sums up the description of the Almighty. Allah (SWT) is the Lord, the Creator, the Omnipotent, the Omniscient, the Omnipresent, the Sustainer, and providence is only from Him. Only Allah (SWT) is Eternal. He gives life and takes it away, forgives sins and punishes wrongdoers; He is All-Knowing, and nothing is hidden from Him. Therefore, Allah (S.W.T) is the only one worthy of worship.