Musnad Ahmad 30:901

I read to Abd al-Rahman: Malik, from Suhayl ibn Abi Salih, from his father, from Abu Hurayrah, that the Messenger of Allah, may Allah bless him and grant him peace, said: "When the Muslim servant — or the believer — performs ablution and washes his face, every sin he looked at with his eyes exits from his face with the water — or with the last drop of water, or something similar. When he washes his hands, every sin his hands committed exits from his hands with the water — or with the last drop of water — until he emerges purified of sins."