Fasting is a condition for the validity of obligatory i'tikaf only; as for voluntary i'tikaf, it is not. Aisha (may Allah be pleased with her) said: "The Sunnah for the one in i'tikaf is that he does not visit the sick, does not attend funerals, does not touch a woman, does not engage with her, and does not leave for a need except for what is absolutely necessary, and there is no i'tikaf except with fasting, and there is no i'tikaf except in a congregational mosque." This is found in Sunan Abu Dawood 2: 333, and Sunan Al-Bayhaqi Al-Kabir 4: 321, and Musannaf Abdul Razzaq 3: 168, and similar statements are known only through hearing, and it has not been narrated that the Prophet (peace be upon him) performed i'tikaf without fasting; if it were permissible, he would have done so to teach its permissibility. Aisha (may Allah be pleased with her) also said: The Prophet (peace be upon him) said: "There is no i'tikaf except with fasting," in Al-Mustadrak 1: 606. Al-Tahanawi said in I'laa Al-Sunan 9: 177: Its chain is authentic according to the principle of Al-Suyuti mentioned in the sermon of Kanz Al-A'mal, and Al-Suyuti authenticated it in Al-Jami' Al-Saghir. Qasim ibn Muhammad and Nafi' the freedman of Ibn Umar (may Allah be pleased with them) said: There is no i'tikaf except with fasting. Allah, Glorified and Exalted, says in His Book: (And eat and drink until the white thread of dawn becomes distinct to you from the black thread [of night]. Then complete the fast until the sunset. And do not have relations with them while you are in i'tikaf in the mosques.) Al-Baqarah: 187. Thus, Allah mentioned i'tikaf along with fasting. And if he vows to perform i'tikaf while fasting, he is obliged to perform i'tikaf while fasting; and if it were not a condition, he would not be obliged, just as if he vowed to perform i'tikaf while giving charity of ten dirhams; this is because a vow is only valid if it is of its kind and is an intended obligation; for a servant cannot establish causes or legislate rulings, but he can impose upon himself what Allah has made obligatory. And staying alone is only obligatory within the context of an act of worship, such as sitting in the Tashahhud. And because fasting is the abstention from eating, drinking, and sexual relations, then one of the pillars of fasting, which is abstaining from sexual relations, is a condition for the validity of i'tikaf; likewise, the other pillar, which is abstaining from eating and drinking, is also a condition, as both are equal in being pillars of fasting. If one of the pillars is a condition, then the other is likewise.