In the Holy Qur'an
And your god is one God! There is no God but He; He is the Beneficent the Merciful (2:163)
In the Traditions
The Prophet said, "Truly Allah resembles no 'thing' and no 'thing' resembles Him; everything which enters one's imagination concerning Him is a misinterpretation."
A man asked the Prophet, "O Muhammad, describe for my Thy Lord."
The Prophet answered, "Surely the Creator cannot be described except by that with which He has described Himself - and how should one describe the Creator whom the senses cannot perceive, imaginations cannot attain, thoughts cannot delimit and sight cannot encompass?
Greater is He than what the depictors describe. He is distant in His nearness and near in His distance. He fashions 'howness', so it is not said of Him, 'How'; He determines the 'where', so it is not said of Him, 'Where?.
He sunders 'howness' and 'whereness', so He is "One...The Everlasting Refuge" (112:2), as He has described Himself. But depictors do not attain to his description. "He has not begotten, and has not been begotten, and equal to Him is not anyone" (112:3-4)