Sunan An-Nasai, Chapter: The Book of Purification

that the Messenger of Allah (saw) said: "When the believing slave performs Wudu and rinses his mouth, his sins come out from his mouth. When he sniffs water into his nose and blows it out, his sins come out from his nose. When he washes his face, his sins come out from his face, even from beneath his eyelashes. When he washes his hands, his sins come out from his hands, even from beneath his fingernails. When he wipes his head, his sins come out from his head, even from his ears. When he washes his feet, his sins come out from his feet, even from beneath his toenails. Then his walking to the Masjid and his Salah will earn extra merit for him." (Hasan)