Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "In the time of the Messenger of Allah (peace and blessings be upon him) we used to call it (Surah al-Mulk) 'al-Mani'ah' (the Protector). It is a surah in the Book of Allah; whoever recites it every night has done much and done excellently."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10216