Surah Al Ma'idah Tafseer

"And why should we not believe in Allah and in that which has come to us of the truth And We wish that our Lord will admit us (in Paradise) along with the righteous people."

Such sect of Christians are those mentioned in Allah's statement,

وَإِنَّ مِنْ أَهْلِ الْكِتَـبِ لَمَن يُوْمِنُ بِاللَّهِ وَمَأ أُنزِلَ إِلَيْكُمْ وَمَأ أُنزِلَ إِلَيْهِمْ خَـشِعِينَ للَّهِ

And there are, certainly, among the People of the Scripture, those who believe in Allah and in that which has been revealed to you, and in that which has been revealed to them, humbling themselves before Allah. (3:199)

and,

الَّذِينَ اتَيْنَاهُمُ الْكِتَابَ مِن قَبْلِهِ هُم بِهِ يُوْمِنُونَ

وَإِذَا يُتْلَى عَلَيْهِمْ قَالُوا امَنَّا بِهِ إِنَّهُ الْحَقُّ مِن رَّبِّنَا إِنَّا كُنَّا مِن قَبْلِهِ مُسْلِمِينَ

Those to whom We gave the Scripture before it, they believe in it (the Qur'an). And when it is recited to them, they say, "We believe in it. Verily, it is the truth from our Lord. Indeed even before it we were Muslims." (28:52-53) until,

"We seek not the ignorant." (28:55)

This is why Allah said here