He will be far away from the most pious. (The first Caliph S. Abu Bakr Siddiq)

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.

(We said) 'David, We have made you a caliph in the earth. Judge with justice among people and do not yield to your own preference in case it should lead you from the Path of Allah. Surely, a terrible punishment awaits those who stray from the Path of Allah, because they forget the Day of Reckoning'