New to Islam?
As Muslims we believe that there is only one God, Allah سبحانه وتعالى. We believe that God is One, therefore Allah سبحانه وتعالى can have no plurals. We believe that the belief of polytheism is wrong as it distorts the core muslim belief that Allah سبحانه وتعالى is One.
Because Allah سبحانه وتعالى is One, He must have always been and always will be, He depends upon no one. Because Allah سبحانه وتعالى is One, the universe He created must also be a unity. This is why following the way of Islam, makes muslims a united community (Ummah).
Surah 112 [Al-Ikhlaas (Sincerity)] states,
Say: "He is Allah, the One! " -112:01
Allah, the eternally Besought of all! -112:02
He begetteth not nor was begotten. -112:03
And there is none comparable unto Him. -112:04
This means that we reject the Christian belief of the Trinity and will not allow anything else to interfere with Allah سبحانه وتعالى's Oneness.
The belief in the Oness of Allah سبحانه وتعالى is called Tawhid and is the basis of all of our beliefs about Allah سبحانه وتعالى. It is also the first part of the muslim Shahadah (first pillar, often called the Muslim creed) -'I bear witness that there is no god but Allah سبحانه وتعالى.
We believe that as there is only One God, Allah سبحانه وتعالى, it follows the Allah سبحانه وتعالى created everything. We believe that Allah سبحانه وتعالى created everything in six days, though one day for Allah سبحانه وتعالى is not the same as a day for a normal being, and therefore cannot fit in the timescale of evolution. We as muslims also reject the belief of evolution as we believe that everything has been made directly by Allah for a particular purpose, and nothing came about incidently.
Allah سبحانه وتعالى has made everything present and He has power over all things. He is The Omnipotent. He is All Powerful over everything that has been created and He has planned for every being. No event occurs without the planning and consent of Allah سبحانه وتعالى.
Allah سبحانه وتعالى is The Most Merciful and Compassionate. Allah has not sent man alone in the world to get on with things, He has sent Prophets with Holy books as a means of guidance and success. His Justice shows that He will judge the believers on how well and far they have followed the teachings of the Prophets. We believe that Allah سبحانه وتعالى is All-Forgiving and any action that has been wrong done which have gone against the teaching of the Prophets and the Holy Books should be repented for. Repentance is an individual and very personal action that muslims make directly to Allah سبحانه وتعالى, as He is The One we turn to for everything.
The Sin of Shirk
As we believe that Tawhid (The Oneness of Allah سبحانه وتعالى) is the core belief about Allah, so the greatest sin would be to destort that belief. Shirk means to associate other beings/partners with Allah سبحانه وتعالى, and it is this act of Shirk that is a very big sin. In mosques and muslim homes there are no pictures or statues of images, as it can lead to the act of Shirk.