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 have certainly disbelieved, those who say, “Allah is one of Three[57].” None has the right to be worshiped except One God. If they do not desist from saying this, those who disbelieve from among them will be afflicted with a painful punishment.
The Christians who say that ‘Allah is part of the Trinity: Father, Son and Holy Spirit’ have committed disbelief. Allah is far above such a statement. Allah is not many, but He is only One God Who has no partner. If they do not stop saying such things, a painful punishment will afflict them.