Jean-Jacques Rousseau said this quote

They say that Caliph Omar, when consulted about what had to be done with the library of Alexandria, answered as follows: 'If the books of this library contain matters opposed to the Koran, they are bad and must be burned. If they contain only the doctrine of the Koran, burn them anyway, for they are superfluous.' Our learned men have cited this reasoning as the height of absurdity. However, suppose Gregory the Great was there instead of Omar and the Gospel instead of the Koran. The library would still have been burned, and that might well have been the finest moment in the life of this illustrious pontiff.