"Is it not a sign for them that the scholars of the Children of Israel know it?" meaning those of them who believed. That is: there was a sign for them in their belief in him.

"Yakun" (is) may be read with both the ta' and the ya'. Whoever reads it with the ta' says: "Ayatun" (a sign) in the nominative, meaning: a sign indeed existed for them, considering it a predicate of "kana" (to be).

Muhammad said: Whoever reads it as "Ayatan" (a sign) in the accusative case considers it the predicate of "kana", while the subject is "an..."