Characteristics of Prayer
Bukhari :: Book 1 :: Volume 12 :: Hadith 773
Narrated Ibn 'Abbas:
The Prophet was ordered (by Allah) to prostrate on seven parts and not to tuck up the clothes or hair (while praying). Those parts are: the forehead (along with the tip of nose), both hands, both knees, and (toes of) both feet.
Source materials are from the University of Southern California MSA site|
Hadith eBooks converted from Imaan Star