Musnad Ahmad 30:894

'Abd al-Rahman ibn Mahdi narrated to us, Isra'il narrated to us, from Abu Sinan, from Abu Salih al-Hanafi, from Abu Sa'id al-Khudri and Abu Hurayrah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, Allah has chosen four from speech: 'Subhan Allah' (Glory be to Allah), 'Al-hamdu lillah' (Praise be to Allah), 'La ilaha illa Allah' (There is no god but Allah), and 'Allahu Akbar' (Allah is the Greatest). So whoever says: 'Subhan Allah,' Allah writes for him twenty good deeds, or removes from him twenty bad deeds. And whoever says: 'Allahu Akbar,' then it is the like of that. And whoever says: 'La ilaha illa Allah,' then it is the like of that. And whoever says: 'Al-hamdu lillahi rabbil-'alamin' (Praise be to Allah, Lord of the worlds), from his own self, thirty good deeds are written for him, or thirty bad deeds are removed from him."