Sura al-Māʾidah 5:73

لَّقَدْ كَفَرَ ٱلَّذِينَ قَالُوٓا۟ إِنَّ ٱللَّـهَ ثَالِثُ ثَلَٰثَةٍ وَمَا مِنْ إِلَٰهٍ إِلَّآ إِلَٰهٌ وَٰحِدٌ وَإِن لَّمْ يَنتَهُوا۟ عَمَّا يَقُولُونَ لَيَمَسَّنَّ ٱلَّذِينَ كَفَرُوا۟ مِنْهُمْ عَذَابٌ أَلِيمٌ

llaqad kafara lladhīna qālū inna allāha thālithu thalāthatin wa-mā min ilāhin illā ilāhun wāḥidun wa-in lam yantahū ʿammā yaqūlūna la-yamassanna lladhīna kafarū minhum ʿadhābun alīmun

They do blaspheme who say: Allah is one of three in a Trinity: for there is no god except One Allah. If they desist not from their word (of blasphemy), verily a grievous penalty will befall the blasphemers among them.