“Was it not enough of a sign for them that the Israelite scholars recognise it?”
The masculine referent of yakun refers to the subsequent phrase.
تَكُنْ لَهُمْ آيَةٌ
takun lahum āyatun
“Was it not the case that they had a sign, (namely) that the Israelite scholars recognise it?”
This reading is best explained with an implied pronoun (ḍamīr al-qiṣṣah) which is the subject of takun, then this is followed by an explicating sentence.
Explication
These readings convey the same meaning with slightly different grammar [al-Mahdawi].
He has revealed to you ˹O Prophet˺ the Book in truth, confirming what came before it, as He revealed the Torah and the Gospel
Explication
These readings convey the same meaning with slightly different grammar [al-Mahdawi].