It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whenever a servant performs ablution, his sins come out from his hands; then when he washes his face, his sins come out from his face; then when he washes his forearms, his sins come out from his forearms; then when he wipes his head, his sins come out from his head; then when he washes his feet, his sins come out from his feet."
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7953