Malik was asked whether someone who went into a mosque to doitikaf for the last ten days of Ramadan and stayed there for a day ortwo but then became ill and left the mosque, had to do itikaf for thenumber of days that were left from the ten, or not, and if he did haveto do so, then what month should he do it in, and he replied, "Heshould make up whatever he has to do of the itikaf when he recovers,whether in Ramadan or otherwise. I have heard that the Messenger ofAllah, may Allah bless him and grant him peace, once wanted to doitikaf in Ramadan, but then came back without having done so, and thenwhen Ramadan had gone, he did itikaf for ten days in Shawwal.Some one who does itikaf voluntarily in Ramadan and some one who hasto do itikaf are in the same position regarding what is halal for themand what is haram. I have not heard that the Messenger of Allah, mayAllah bless him and grant him peace, ever did itikaf other thanvoluntarily."Malik said, that if a woman did itikaf and thenmenstruated during her itikaf, she went back to her house, and, whenshe was pure again she returned to the mosque, at whatever time it wasthat she became pure. She then continued her itikaf from where sheleft off. This was the same situation as with a woman who had to fasttwo consecutive months, and who menstruated and then became pure. Shethen continued the fast from where she had left off and did not delaydoing so.
USC-MSA web (English) reference: Book 19, Hadith 8