Sahih Muslim Book 6, Hadith Number 2395.
Chapter : The months of Id are not incomplete.
‘Abd Ar-Rahman b. Abu Bakra reported on the authority of Abu Bakra that the Apostle of Allah (may peace be upon him) had said: The months of ‘Id are not incomplete. And in the Hadith narrated by Khalid (the words are): “The months, of ‘Id are Ramadan and Dhu’l-Hijja.”