Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: I fasted twenty-nine days (of Ramadan) with the Messenger of Allah (peace and blessings be upon him) more often than I fasted thirty days with him (peace and blessings be upon him).
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10490