﴿ ذَٰلِكَ عِيسَى ٱبْنُ مَرْيَمَ ۚ قَوْلَ ٱلْحَقِّ ٱلَّذِى فِيهِ يَمْتَرُونَ ﴾

“SUCH WAS, in the words of truth, Jesus the son of Mary, about whose nature they so deeply disagree.”

That is Jesus son of Mary a statement of truth read qawlu’l-haqqi as the predicate of an implied subject in other words ‘the statement of the son of Mary is a statement of truth’; or read qawla’l-haqqi because of it being the object of an implied verb qultu ‘I say’ meaning ‘I say a statement of truth’ concerning which they are in doubt yamtarūna derives from the infinitive al-mirya — they are the Christians who say ‘Indeed Jesus is the son of God’; but they lie.