Sahih Muslim , Book 4, Hadith 1455 (USC-MSA) ⓘ
This hadith has been narrated by Qatada, but here no mention has been made of" There is no explation for it except this."
وَحَدَّثَنَاهُ يَحْيَى بْنُ يَحْيَى، وَسَعِيدُ بْنُ مَنْصُورٍ، وَقُتَيْبَةُ بْنُ سَعِيدٍ، جَمِيعًا عَنْ أَبِي عَوَانَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم وَلَمْ يَذْكُرْ " لاَ كَفَّارَةَ لَهَا إِلاَّ ذَلِكَ " .
also referenced under: Book 5, Hadith 403 (In-Book) & Hadith 684 (Reference)