If humans are born pure and innocent, then from where does evil come? And what does the Holy Qur'an say about the Bible?

Man is born with a sound natural disposition (fitra), but factors exist that push him towards falsehood and evil, among them: parents, environment, and Iblis and his soldiers. The Quran mentions that the original Torah and Gospel were revealed by Allah, but they were later distorted and altered. Specific principles should be observed when responding to disbelievers and People of the Book, with a preference for men inviting men and women inviting women to avoid fitna (strife/temptation).