Sahih Muslim Book 2, Hadith Number 484.

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 Hazim reported: I was (standing) behind Abu Huraira and he was performing the ablution for prayer. He extended the (washing) of his hand that it went up to his armpit. I said to him: O Abu Huraira, what is this ablution? He said: O of the tribe of Faruukh, you are here; if I knew that you were here, I would have never performed ablution like this; I have heard my Friend (may peace be upon him) say. In a believer adornment would reach the places where ablution reaches.