Musannaf Ibn Abi Shayba 21:85

Ibn Numayr narrated to us, from Hisham ibn Urwah, from Aisha, that the Messenger of Allah, may Allah bless him and grant him peace, used to supplicate: "O Allah, wash away my sins with the water of snow and hail, and cleanse my heart of sins as You have cleansed the white garment of filth. And distance between me and my sins as You have distanced between the East and the West."