Musnad Ahmad 799:146

Waki’ narrated to us, Sufyan narrated to us, from Salamah ibn Kuhayl, from Hilal ibn Yasaf, from Samurah ibn Jundab, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best of speech after the Quran—and it is from the Quran—is four, it does not harm you with which of them you begin: 'Subhan Allah' (Glory be to Allah), 'Al-hamdulillah' (Praise be to Allah), 'La ilaha illa Allah' (There is no god but Allah), and 'Allahu Akbar' (Allah is the Greatest)."