Imam Malik's Muwatta, Chapter: Itikaf in Ramadan

Ziyad related to me from Malik from Ibn Shihab from Amra bint Abd ar-Rahman from A'isha that the Messenger of Allah, may Allah bless him and grant him peace, once wanted to do itikaf, and when he went off to the place where he wanted to do itikaf he found some tents there, which were A'isha's tent, Hafsa's tent, and Zaynab's tent. When he saw them he asked about them and someone told him that they were the tents of A'isha, Hafsa and Zaynab. The Messenger of Allah, may Allah bless him and grant him peace, said, "Do you think them devout?" Then he left, and did not do itikaf until Shawwal, when he then did it for ten days.