(a) Talhah (may Allah have mercy on him) narrates from his grandfather (may Allah be pleased with him) that he saw the Prophet (peace and blessings be upon him) performing ablution; he (peace and blessings be upon him) wiped his head and his ears and passed his hands over his nape.
(b) Layth bin Abi Sulaym (may Allah have mercy on him) said: He wiped his head until he reached the beginning of the nape; but he did not mention passing the hands over the nape.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 278