They have certainly disbelieved who say, "Allah is the Messiah, the son of Mary" while the Messiah has said, "O Children of Israel, worship Allah, my Lord and your Lord." Indeed, he who associates others with Allah - Allah has forbidden him Paradise, and his refuge is the Fire. And there are not for the wrongdoers any helpers.  

لَقَدْ كَفَرَ الَّذِينَ قَالُوا إِنَّ اللَّهَ هُوَ الْمَسِيحُ ابْنُ مَرْيَمَ ۖ وَقَالَ الْمَسِيحُ يَا بَنِي إِسْرَائِيلَ اعْبُدُوا اللَّهَ رَبِّي وَرَبَّكُمْ ۖ إِنَّهُ مَنْ يُشْرِكْ بِاللَّهِ فَقَدْ حَرَّمَ اللَّهُ عَلَيْهِ الْجَنَّةَ وَمَأْوَاهُ النَّارُ ۖ وَمَا لِلظَّالِمِينَ مِنْ أَنْصَارٍ  

They have certainly disbelieved who say, "Allah is the third of three." And there is no god except one God. And if they do not desist from what they are saying, there will surely afflict the disbelievers among them a painful punishment.  

لَقَدْ كَفَرَ الَّذِينَ قَالُوا إِنَّ اللَّهَ ثَالِثُ ثَلَاثَةٍ ۘ وَمَا مِنْ إِلَٰهٍ إِلَّا إِلَٰهٌ وَاحِدٌ ۚ وَإِنْ لَمْ يَنْتَهُوا عَمَّا يَقُولُونَ لَيَمَسَّنَّ الَّذِينَ كَفَرُوا مِنْهُمْ عَذَابٌ أَلِيمٌ  

So will they not repent to Allah and seek His forgiveness? And Allah is Forgiving and Merciful.  

أَفَلَا يَتُوبُونَ إِلَى اللَّهِ وَيَسْتَغْفِرُونَهُ ۚ وَاللَّهُ غَفُورٌ رَحِيمٌ