Say, "What thing is greatest in testimony?" Say, "Allāh is witness between me and you. And this Qur’ān was revealed to me that I may warn you thereby and whomever it reaches. Do you [truly] testify that with Allāh there are other deities?" Say, "I will not testify [with you]." Say, "Indeed, He is but one God, and indeed, I am free of what you associate [with Him]."

Sahih International