I say, and with God's success: I'tikaf is only obligatory in the case of a vow, whether the vow is explicit, like saying: 'It is upon me to perform I'tikaf for such and such,' or conditional, like saying: 'If God heals my patient so-and-so, then I will perform I'tikaf for such and such.' Refer to: Al-Hadiyyah Al-'Ala'iyyah, p. 183, and God knows best.