I say, and with God's success: If the wiping occurs on the washed area of three fingers from the smallest finger of the hand or more, it is permissible for him to wipe; otherwise, it is not permissible. This is because it is a condition for the permissibility of wiping that the shoe is occupied in the area of wiping: that he does not wipe on the area empty of the foot if he has lost a part of his foot. If the shoe is not occupied in the area of wiping, he is not allowed to wipe; because when he wipes on the area empty of the foot, the wiping does not occur in its proper place, which is the top of the foot, thus it does not prevent the transmission of the event to the foot. See: Nihayat al-Mirad, p. 380, and God knows best.