(3) Purification
كتاب الطهارة
(1a) Chapter: Section 1
الفصل الأول
Mishkat al-Masabih 286 
‘Uthman reported God’s messenger as saying, “When the time for a prescribed prayer comes, if any Muslim observes proper ablution, humility and bowing, it will be an expiation for his past sins, so long as he has not committed a major sin; and that means for all time.” Muslim transmitted it.
وَعَنْ عُثْمَانَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَا مِنَ امْرِئٍ مُسْلِمٍ تَحْضُرُهُ صَلَاةٌ مَكْتُوبَةٌ فَيُحْسِنُ وُضُوءَهَا وَخُشُوعَهَا وَرُكُوعَهَا إِلَّا كَانَتْ كَفَّارَةً لِمَا قَبْلَهَا مِنَ الذُّنُوبِ مَا لَمْ يُؤْتِ كَبِيرَةً وَذَلِكَ الدَّهْرَ كُلَّهُ» . رَوَاهُ مُسلم
 صَحِيح  (الألباني)حكم :
Reference : Mishkat al-Masabih 286
In-book reference : Book 3, Hadith 5