Sunan an-Nasa'i, Volume 1, Book 2, Hadith 335 (DarusSalam) ⓘ

It was narrated that Abu Hurairah said: "The Messenger of Allah would say: [1] 'Allahummaghsil khatayaya bi-ma'ith-thalj wal-barad (O Allah, wash away my sins with the water of snow and hail).'" [1] That is at the beginning of Salah as is clear from the remainder of the narration which preceded under No. 60.

أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ أَنْبَأَنَا جَرِيرٌ، عَنْ عُمَارَةَ بْنِ الْقَعْقَاعِ، عَنْ أَبِي زُرْعَةَ بْنِ عَمْرِو بْنِ جَرِيرٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ اللَّهُمَّ اغْسِلْنِي مِنْ خَطَايَاىَ بِالثَّلْجِ وَالْمَاءِ وَالْبَرَدِ ‏" ‏ ‏.‏