قُلْ أَىُّ شَىْءٍ أَكْبَرُ شَهَـٰدَةًۭ ۖ قُلِ ٱللَّهُ ۖ شَهِيدٌۢ بَيْنِى وَبَيْنَكُمْ ۚ وَأُوحِىَ إِلَىَّ هَـٰذَا ٱلْقُرْءَانُ لِأُنذِرَكُم بِهِۦ وَمَنۢ بَلَغَ ۚ أَئِنَّكُمْ لَتَشْهَدُونَ أَنَّ مَعَ ٱللَّهِ ءَالِهَةً أُخْرَىٰ ۚ قُل لَّآ أَشْهَدُ ۚ قُلْ إِنَّمَا هُوَ إِلَـٰهٌۭ وَٰحِدٌۭ وَإِنَّنِى بَرِىٓءٌۭ مِّمَّا تُشْرِكُونَ

Say, "What thing is greatest in testimony?" Say, "Allah is witness between me and you. And this Qur'an was revealed to me that I may warn you thereby and whomever it reaches. Do you [truly] testify that with Allah 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]."

— Al-An‘ām 6:19