Sayyidah Aishah (may Allah be pleased with her), the wife of the Prophet (peace and blessings be upon him), narrates that he (peace and blessings be upon him) used to observe i'tikaf in the last ten (days) of Ramadan until Allah took him (peace and blessings be upon him) in death; then his wives continued to observe i'tikaf after him (peace and blessings be upon him).
The Sunnah for the one in i'tikaf is that he does not go out except for a need that cannot be avoided, does not visit the sick, does not touch a woman nor have intimate contact with her; there is no i'tikaf except in a congregational mosque; and the Sunnah for one observing i'tikaf is that he also fasts.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8571