Pagans indeed are those who say that God is a third of a trinity. There is no god except the one god. Unless they refrain from saying this, those who disbelieve among them will incur a painful retribution.
لَقَد كَفَرَ الَّذينَ قالوا إِنَّ اللَّهَ ثالِثُ ثَلٰثَةٍ وَما مِن إِلٰهٍ إِلّا إِلٰهٌ وٰحِدٌ وَإِن لَم يَنتَهوا عَمّا يَقولونَ لَيَمَسَّنَّ الَّذينَ كَفَروا مِنهُم عَذابٌ أَليمٌ
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