The Prophet ﷺ used to say, "Allah, wash away my sins with the water of snow and hail, and cleanse my heart of sins as a white garment is cleansed of filth."
أخبرنا إسحق بن إبراهيم قال أنبأنا جرير عن هشام بن عروة عن أبيه
كان النبي ﷺ يقول اللهم اغسل خطاياي بماء الثلج والبرد ونق قلبي من الخطايا كما نقيت الثوب الأبيض من الدنس
Agreed upon. Bukhari narrated it in the Book of Supplications, Chapter on Seeking Refuge from Extreme Old Age, etc., hadith (6375), and Muslim in the Book of Remembrance and Supplication, Chapter on Supplications and Seeking Refuge, (589) after hadith (2705), from the hadith of Hisham, at length, and it is in Al-Kubra, [(61)]