Sahih Bukhari, Chapter: Retiring to a Mosque for Remembrance of Allah (Itikaf)

Aisha said, "the Prophet (SAW) used to practice Itikaf in the last ten days of Ramadan and I used to pitch a tent for him, and after offering the morning prayer, he used to enter the tent." Hafsa asked the permission of Aisha to pitch a tent for her and she allowed her and she pitched her tent. When Zainab bint Jahsh saw it, she pitched another tent. In the morning the Prophet noticed the tents. He said, 'What is this?" He was told of the whole situation. Then the Prophet said, "Do you think that they intended to do righteousness by doing this?" He therefore abandoned the Itikaf in that month and practiced Itikaf for ten days in the month of Shawwal."