Sahih Bukhari, Chapter: Pilgrimage (Hajj)

Allah's Apostle said, "O Allah! Be merciful to those who have their head shaved." The people said, "O Allah's Apostle! And (invoke Allah for) those who get their hair cut short." The Prophet said, "O Allah! Be merciful to those who have their head shaved." The people said, "O Allah's Apostle! And those who get their hair cut short." The Prophet said (the third time), "And to those who get their hair cut short." Nafi said that the Prophet had said once or twice, "O Allah! Be merciful to those who get their head shaved," and on the fourth time he added, "And to those who have their hair cut short."