Musnad Ahmad

Humran says that once Sayyiduna Uthman (may Allah be pleased with him) called for water to perform ablution. He rinsed his mouth, put water in his nose, washed his face three times, washed both arms three times, wiped his head, and also wiped over the upper part of his feet, and then he laughed. Then he asked his companions, "Why do you not ask me the reason for my laughter?" The people said, "O Commander of the Faithful! You tell us why you laughed." He said, "I saw the Prophet (peace and blessings be upon him) call for water in the same way, sit near this place, and perform ablution in the same manner as I did. Then the Prophet (peace and blessings be upon him) also laughed and asked his companions, 'Why do you not ask me the reason for my laughter?' The noble Companions (may Allah be pleased with them) asked, 'O Messenger of Allah! What made you laugh?' He said, 'When a person calls for water to perform ablution and washes his face, Allah forgives all the sins committed by his face. When he washes his arms, the same happens. When he wipes his head, the same happens. And when he cleans his feet, the same happens.'"