Q: In tayammum, is it necessary to wipe our forehead by the palms, or it is valid by fingers? what is the rule of prayer said after doing tayammum wiping the forehead by the fingers?
A: In tayammum, wiping should be done by the inner surface of the hands (from the wrists to the tip of fingers). First, you wipe the forehead and its both sides from the hair line to (including) eyebrows by both hands. Then, you move the palm of your left hand on the back of right hand and the palm of your right hand on the back of left hand. By obligatory caution, hit your hands on the ground and move the palm of your left hand on the back of right hand and the palm of your right hand on the back of left hand again. Otherwise, the tayammum is not valid and you should say the prayers performed for sure after invalid tayammum again.