It was narrated from Khalid bin Walid, Yazid bin Abu Sufyan, Shurahbil bin Hasanah and 'Amr bin 'As that:
They all heard the Messenger of Allah say: 'Complete the ablution. Woe to the heels because of Hell-fire." (IT)
English reference (IT): Vol. 1, Book 1, Hadith 455 (IT)
Arabic reference (IT): Book 1, Hadith 491 (IT)