Qur'an 5:73

لَّقَدْ كَفَرَ ٱلَّذِينَ قَالُوٓا۟ إِنَّ ٱللَّهَ ثَالِثُ ثَلَـٰثَةٍ ۘ وَمَا مِنْ إِلَـٰهٍ إِلَّآ إِلَـٰهٌ وَٰحِدٌ ۚ وَإِن لَّمْ يَنتَهُوا۟ عَمَّا يَقُولُونَ لَيَمَسَّنَّ ٱلَّذِينَ كَفَرُوا۟ مِنْهُمْ عَذَابٌ أَلِيمٌ

They surely disbelieve who say: Lo! Allah is the third of three; when there is no God save the One Allah. If they desist not from so saying a painful doom will fall on those of them who disbelieve.