Tawhid

Tawhid (Arabic: توحيد‎, tawḥīd, meaning "unification of God (Allāh)"; also romanized as Tawheed, Tauhid, Tauheed or Tevhid) is the indivisible unification concept of monotheism in Islam. Tawhid is the religion's central and single most important concept, upon which a Muslim's entire religious adherence rests. It unequivocally holds that God (Arabic: الله Allāh) is one (Al-ʾAḥad) and single (Al-Wāḥid).

Tawhid constitutes the foremost article of the Muslim profession of submission. The first part of the shahada (the Islamic declaration of faith) is the declaration of belief in the unification of God. To attribute divinity to anything or anyone else, is shirk – an unpardonable sin according to the Qur'an, unless repented afterwards. Muslims believe that the entirety of the Islamic teaching rests on the principle of Tawhid.

From an Islamic standpoint, there is an uncompromising nondualism at the heart of the Islamic beliefs (aqidah) which is seen as distinguishing Islam from other major religions. Moreover, Tawhid requires Muslims not only to avoid worshiping multiple gods, but also to relinquish striving for money, social status or egoism, as well as attributing all success and worth to other than God, as this is seen as making an idol of the self.

The Qur'an asserts the existence of a single and absolute truth that transcends the world; a unique, independent and indivisible being, who is independent of the entire creation. God, according to Islam, is a universal God, rather than a local, tribal, or parochial one—God is an absolute, who integrates all affirmative values.

Islamic intellectual history can be understood as a gradual unfolding of the manner in which successive generations of believers have understood the meaning and implications of professing God's Unity. Islamic scholars have different approaches toward understanding it. Islamic theology, jurisprudence, philosophy, Sufism, even to some degree the Islamic understanding of natural sciences, all seek to explain at some level the principle of tawhid.

The classical definition of tawhid was limited to declaring or preferring belief in one God and the unity of God. Although the monotheistic definition has persisted into modern Arabic, it is now more generally used to connote "unification, union, combination, fusion; standardization, regularization; consolidation, amalgamation, merger".

Chapter 112 of the Quran, titled Al-'Ikhlās (The Sincerity) reads:

Say, "He is Allah—One;
Allah—the Sustainer.
He has never had offspring, nor was He born.
And there is none comparable to Him."