Sahih Muslim
The Book of Fasting (Kitab Al-Sawm)
Book Number: 006 / Hadith Number: 2395
'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."