Ibrahim bin Abdullah bin Hunayn (may Allah have mercy on him) narrates that Abdullah bin Abbas (may Allah be pleased with them both) and Miswar bin Makhramah (may Allah be pleased with him) differed over whether the muhrim may wash his head with water when not in a state of major impurity (janabah). So the two of them sent me to Abu Ayyub (may Allah be pleased with him), who was at one of the watering places of Makkah, to ask him about this matter. I came to him and found Abu Ayyub (may Allah be pleased with him) washing his head between the two posts of a well, screening himself with a cloth. I asked him, and he lowered the cloth with his hand until his head appeared; then he rubbed his head and hair with both his hands, moving his hands forward through his hair and bringing them back, then he said: This is how I saw the Messenger of Allah (peace and blessings be upon him) bathing while he was in the state of ihram. Ibrahim (may Allah have mercy on him) says: Then I went back to them and told them.
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3963