Sunan at-Tirmidhi (Jami-al-Tirmidhi), Chapter: Taharah (Purification)

reported that the Prophet (SAW) said, "When a Muslim slave", or, "a Believer washes his face while performing ablution then, with the water, or the last drop of water, all his sins committed with his eyes are washed away. When he washes his hands then all sins commited with them are washed away with water or the last drop of water till comes out pure from sins." [Ahmed8026, Muslim 244]