Aļļaah said in the Qur’aan,
قُلْ هُوَ اللَّهُ أَحَدٌ
Meaning: “Say! <O Muĥammad> He is Aļļaah, He is One.” (Al-Ikħlaaş, 1)
The word “One” here is absolute in meaning, as the statement is absolute. In other words, it is impossible that He should have an equal in His self, actions or attributes, or a partner or a part. It is also impossible that Aļļaah should have two attributes of the same kind, e.g. two powers, or two attributes of knowledge.
The Imaam Aĥmad ibn Ĥanbal explained: “Aļļaah U is One, not in the sense of a number; it is impossible that He should be divisible or have parts; He is One in every sense of the meaning, whereas everything else is one in one sense, but not in others.”
For example, I am one person, but I am one in the shared sense of being one among many of a kind. In addition, I have many attributes in common with others, such as taking up space, so I have partners in my attributes as well. I am also a collection of body parts, and all of my body parts are divisible. Accordingly, I am not one in an absolute sense, but in a composed, or shared, sense. That is, my uniqueness is only a created kind of uniqueness.
Abuu Ĥaniifah similarly said, “God is One, not in a numerical sense, but in the sense that He has no partner. He neither begets, nor was He begotten, and there is none like Him. He neither resembles any of His creation, nor does anything among His creation resemble Him.”