Sunan Ibn Majah, Book 1, Hadith 641 (In-Book) ⓘ

Abu Ayyub Al-Ansari narrated that: The Prophet said: "The five daily prayers, from one Friday to the next, and fulfilling the trust are all expiation for whatever (sins) come between them." I said: "What is fulfilling the trust?" He said: Having a bath to cleanse oneself from sexual impurity, for under every hair there is the state of sexual impurity."

حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ، حَدَّثَنَا يَحْيَى بْنُ حَمْزَةَ، حَدَّثَنِي عُتْبَةُ بْنُ أَبِي حَكِيمٍ، حَدَّثَنِي طَلْحَةُ بْنُ نَافِعٍ، حَدَّثَنِي أَبُو أَيُّوبَ الأَنْصَارِيُّ، أَنَّ النَّبِيَّ ـ صلى الله عليه وسلم ـ قَالَ ‏"‏ الصَّلَوَاتُ الْخَمْسُ وَالْجُمُعَةُ إِلَى الْجُمُعَةِ وَأَدَاءُ الأَمَانَةِ كَفَّارَةٌ لِمَا بَيْنَهَا ‏"‏ ‏.‏ قُلْتُ وَمَا أَدَاءُ الأَمَانَةِ قَالَ ‏"‏ غُسْلُ الْجَنَابَةِ فَإِنَّ تَحْتَ كُلِّ شَعَرَةٍ جَنَابَةً ‏"‏ ‏.‏