Sahih Bukhari Volume 2, Book 26, Hadith Number 786.

Narated By Abu Huraira : Allah’s Apostle said, “O Allah! Forgive those who get their heads shaved.” The people asked. “Also those who get their hair cut short?” The Prophet said, “O Allah! Forgive those who have their heads shaved.” The people said, “Also those who get their hair cut short?” The Prophet (invoke Allah for those who have their heads shaved and) at the third time said, “also (forgive) those who get their hair cut short.”