Quran 6:19 Al-An'am, ayah 19 of 165

قُلْ أَىُّ شَىْءٍ أَكْبَرُ شَهَـٰدَةً ۖ 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 إِلَـٰهٌ وَٰحِدٌ وَإِنَّنِى بَرِىٓءٌ مِّمَّا تُشْرِكُونَ ۝١٩

6:19 Say (O Muhammad): What thing is of most weight in testimony? Say: Allah is Witness between me and you. And this Qur'an hath been inspired in me, that I may warn therewith you and whomsoever it may reach. Do ye in sooth bear witness that there are gods beside Allah? Say: I bear no such witness. Say: He is only One Allah. Lo! I am innocent of that which ye associate (with Him).