'Abdullah bin 'Amr said:
"The Messenger of Allah saw some people performing ablution, and their heels were dry. He said: 'Woe to the heels because of Hell-fire, perform ablution properly!'" (AR)
English reference (AR): Vol. 1, Book 1, Hadith 450 (AR)
Arabic reference (AR): Book 1, Hadith 486 (AR)