Sunan Ibn Majah, Chapter: The Chapters on Etiquette

"I came to the Messenger of Allah (saw) and said: 'O Messenger of Allah, tell me of a (good) deed, for I have become old and weak and overweight.' He said: 'Proclaim the greatness of Allah (say Allahu Akbar) one hundred times, praise Allah (say Al-Hamdu Lillah) one hundred times, and glorify Allah (say Subhan-Allah) one hundred times. (That is) better than one hundred horses bridled and saddled for the sake of Allah, better than one hundred sacrificial camels, and better than (freeing) one hundred slaves.'"