I say, and with God's success: I'tikaf is not valid without intention; because intention is a condition for the validity of I'tikaf. The intended act of worship is not valid without intention. The Prophet (peace be upon him) said: "Actions are judged by intentions." Refer to: Bada'i' al-Sana'i' 2: 109, and Al-Hadiyya Al-Alaiyya p. 183, and God knows best.