Surah 2. Al-Baqara, Ayah 146

The People of the Book should have known all this as well as "they knew their own sons", as their past traditions and teaching should have made them receptive of the new message. Some commentators construe the demonstrative pronoun "this" to refer to the Apostle. In that case the interpretation would be: The People of the Book know Muhammad as well as they know their own sons; they know him to be true and upright; they know him to be in the line of Abraham; they know him to correspond to the description of the prophet foretold among themselves; but selfishness induces some of them to act against their own knowledge and conceal the truth.