Narrated Abu Huraira:
Some poor people came to the Prophet (sallallahu alayhi wa salam) and said, "The wealthy people will get higher grades and will have permanent enjoyment and they pray like us and fast as we do. They have more money by which they perform the hajj, and 'Umra; fight and struggle in Allah's Cause and give in charity." The Prophet (sallallahu alayhi wa salam) said, "Shall I not tell you a thing upon which if you acted you would catch up with those who have surpassed you? Nobody would overtake you and you would be better than the people amongst whom you live except those who would do the same. Say "Sub-han-al-lah", "Alhamdu-lillah" and "Allahu Akbar" thirty three times each after every (compulsory) prayer." We differed and some of us said that we should say, "Subhan-al-lah" thirty three times and "Alhamdu lillah" thirty three times and "Allahu Akbar" thirty four times. I went to the Prophet who said, "Say, "Subhan-al-lah" and "Alhamdu lillah" and "Allahu Akbar" all together for thirty three times."
(Sahih Bukhari, Book 12, Number 804)