Sahih Muslim
The Book of Pilgrimage (Kitab Al-Hajj)
Book Number: 007 / Hadith Number: 2984
Abdullah b. Umar (Allah be pleased with him) reported Allah's Messenger (may peace be upon him) as having observed: O Allah, have mercy upon those who get their heads shaved. They (the Companions) said: Messenger of Allah, (what about those) who have got their hair clipped? He said: O Allah, have mercy upon those who have got their heads shaved. They (again) said: Allah's Messenger, (what about those) who have got their hair clipped? Thereupon he said: (O Allah, have mercy upon those) who have got their hair clipped.