I say, and with Allah's success: It is forbidden for the one in i'tikaf to engage in intercourse and its causes; due to His saying, the Exalted: {And do not approach them while you are in i'tikaf in the mosques} Al-Baqarah: 187. Thus, its causes are included, which are touching and kissing; because intercourse is prohibited by text, it extends to its causes. Therefore, if the one in i'tikaf has intercourse in a manner less than penetration, or kisses, or touches and then ejaculates, his i'tikaf is invalidated even if he forgets; because it is akin to intercourse. However, if he does not ejaculate, it does not invalidate it; because it is not akin to intercourse. For this reason, it does not invalidate fasting. Refer to: Al-Tahbiyin 1: 352, Al-Wiqayah p. 245, and Al-Mabsut 3: 123, and Allah knows best.