Surah Al-Mai'dah (The Spread Table), Verse 73

لَقَدْ كَفَرَ الَّذِیْنَ قَالُوْۤا اِنَّ اللّٰهَ ثَالِثُ ثَلٰثَةٍ وَمَا مِنْ اِلٰهٍ اِلَّاۤ اِلٰهٌ وَّاحِدٌ وَاِنْ لَّمْ یَنْتَهُوْا عَمَّا یَقُوْلُوْنَ لَیَمَسَّنَّ الَّذِیْنَ كَفَرُوْا مِنْهُمْ عَذَابٌ اَلِیْمٌ ۟

laqad kafaral lazeena qaalooo innal laaha saalisu salaasah; wa maa min ilaahin illaaa Ilaahunw Waahid; wa illam yantahoo 'ammaa yaqooloona layamas sannal lazeena kafaroo minhum 'azaabun aleem

“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.”

Quran 5:73 (Yusuf Ali Translation)