Your God is One God. There is no god but Him, the All-Merciful, the Most Merciful. (Qur'an, 2:163)
Allah bears witness that there is no god but Him, as do the angels and the people of knowledge, upholding justice. There is no god but Him, the Almighty, the All-Wise. (Qur'an, 3:18)
Allah says, 'Do not take two gods. He is only One God. So dread Me alone." (Qur'an, 16:51)
Say: 'He is Allah, Absolute Oneness. (Qur'an, 112:1)
He is Allah. There is no god but Him. Praise be to Him in this world and the hereafter. Judgement belongs to Him. You will be returned to Him. (Qur'an, 28:70)