The unity of Allah is expressed in Suratul-Ikhlas. This surah is the 112th chapter of the Quran and it emphasizes the oneness of Allah. It is also known as "Al-Tawheed" which means "the declaration of the oneness of God."
The Surah begins with the statement "Say: He is Allah, the One and Only; Allah, the Eternal, Absolute; He begetteth not, nor is He begotten; And there is none like unto Him."
This surah explains that Allah is the only true God, and there is no other deity worthy of worship. It also emphasizes that Allah is eternal and absolute, and that He has no children or parents. In Islam, the concept of the oneness of Allah is known as "Tawheed," and it is the foundation of Islamic faith.
Thus, the Suratul-Ikhlas is a very important chapter in the Quran for Muslims as it emphasizes the core principle of Tawheed, which is the belief in the unity and oneness of Allah. It is recited in various Islamic rituals such as the daily prayers and during special occasions such as funerals.