Now it's very easy to assume that those books, because they were from a library called Bait al-Hikma, were Muslim books, but that's not the case because the caliph that built that library, his name was al-Ma'mun -- he was Harun al-Rashid's son.
E' molto facile pensare che quei libri, provenendo da una biblioteca chiamata al-Hikma, fossero libri musulmani ma in realtà non è così perché il califfo che l'aveva costruita, il suo nome era al-Ma'mum, era il figlio di Harun al-Rashid.