Sahih Muslim Book 2, Hadith Number 482.

Chapter : It is commendable to include forehead in washing the face and elbow and ankle in washing the hands and feet, while performing ablution.

Abu Huraira reported: The Messenger of Allah (may peace be upon him) came to the graveyard and said: Peace be upon you ! the abode of the believing people and we, if God so wills, are about to join you. I love to see my brothers. They (the hearers) said: Aren’t we your brothers – Messenger of Allah? He said: You are my companions, and our brothers are those who have, so far, not come into the world. They said: Messenger of Allah, how would you recognise those persons of your Ummah who have not yet been born? He said: Supposing a man had horses with white blazes on fore- heads and legs among horses which were all black, tell me, would he not recognise his own horses? They said: Certainly. Messenger of Allah. He said: They would come with white faces and arms and legs owing to ablution, and I would arrive at the Cistern before them. Some people would be driven away from my Cistern as the stray camel is driven away. I would call out. Come; come. Then it would be said (to me): These people changed themselves after you, and I would say: Be off, be off.