Sahih Bukhari
Fighting for the Cause of Allah (Jihaad)
Volume: 004 / Book Number: 052 / Hadith Number: 81
Narrated Anas bin Malik
In the life-time of the Prophet, Abu Talha did not fast because of the Jihad, but after the Prophet died I never saw him without fasting except on 'Id-ul-Fitr and 'Id-ul-Aclha.