Is it permissible to wipe the head with the width of a finger (i.e., with only the two index fingers touching), and is it permissible to wipe with the back of the hand?

Scholars differ concerning the validity of wiping the head with one finger. The majority opinion is that wiping with one finger is valid. In fact, the Shafi'is maintained its validity even with part of a finger. The Hanafis disagreed, stating that wiping is not valid with fewer than three fingers. The easier and more cautious approach is to spread the water over both palms when wiping the head.