Sahih Bukhari
Retiring to a Mosque for Remembrance of Allah (Itikaf)
Volume: 003 / Book Number: 033 / Hadith Number: 246
Narrated 'Aisha:
(the wife of the Prophet) Allah's Apostle used to let his head in (the house) while he was in the mosque and I would comb and oil his hair. When in Itikaf he used not to enter the house except for a need.