Yahya related to me from Malik from Nafi from Abdullah ibn Umarthat the Messenger of Allah, may Allah bless him and grant him peace,said, "A man who knows the Qur'an well is like a man who has a hobbledcamel. If he takes care of it, he keeps it, and if he lets it go, itgets away."
USC-MSA web (English) reference: Book 15, Hadith 6
Arabic reference: Book 15, Hadith 478