The Quran

Preface

۞ لَتَجِدَنَّ أَشَدَّ النّاسِ عَداوَةً لِلَّذينَ آمَنُوا اليَهودَ وَالَّذينَ أَشرَكوا ۖ وَلَتَجِدَنَّ أَقرَبَهُم مَوَدَّةً لِلَّذينَ آمَنُوا الَّذينَ قالوا إِنّا نَصارىٰ ۚ ذٰلِكَ بِأَنَّ مِنهُم قِسّيسينَ وَرُهبانًا وَأَنَّهُم لا يَستَكبِرونَ

Yusuf Ali

Strongest among men in enmity to the believers wilt thou find the Jews and Pagans; and nearest among them in love to the believers wilt thou find those who say,¹ “We are Christians”: because amongst these are men devoted to learning² and men who have renounced the world, and they are not arrogant.

The meaning is not that they merely call themselves Christians, but that they are such sincere Christians that they appreciate Muslim virtues, as did the Abyssinians to whom Muslim refugees went during the persecution in Mecca. (R).
Qissis: I have translated as “devoted to learning,” following the Commentators.
It seems to be a foreign word, possibly Abyssinian rather than Syriac, as the reference seems to be to the Abyssinian Christians. Their real devotion to learning and the renunciation of the world by the Monastic Orders are contrasted with the hypocrisy and arrogance of the Pharisees and Scribes.