Sahih al-Bukhari 160
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · The washing of the parts thrice while performing ablution
After performing the ablution 'Uthman said, "I am going to tell you a Hadith which I would not have told you, had I not been compelled by a certain Holy Verse (the sub narrator 'Urwa said:
وَعَنْ إِبْرَاهِيمَ ، قَالَ قَالَ صَالِحُ بْنُ كَيْسَانَ قَالَ ابْنُ شِهَابٍ وَلَكِنْ عُرْوَةُ يُحَدِّثُ عَنْ حُمْرَانَ ،، فَلَمَّا تَوَضَّأَ عُثْمَانُ قَالَ أَلاَ أُحَدِّثُكُمْ حَدِيثًا لَوْلاَ آيَةٌ مَا حَدَّثْتُكُمُوهُ، سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " لاَ يَتَوَضَّأُ رَجُلٌ فَيُحْسِنُ وُضُوءَهُ، وَيُصَلِّي الصَّلاَةَ إِلاَّ غُفِرَ لَهُ مَا بَيْنَهُ وَبَيْنَ الصَّلاَةِ حَتَّى يُصَلِّيَهَا ". قَالَ عُرْوَةُ الآيَةُ {إِنَّ الَّذِينَ يَكْتُمُونَ مَا أَنْزَلْنَا مِنَ الْبَيِّنَاتِ} .
This verse is: "Verily, those who conceal the clear signs and the guidance which we have sent down...)" (2:159). I heard the Prophet (ﷺ) saying, 'If a man performs ablution perfectly and then offers the compulsory congregational prayer, Allah will forgive his sins committed between that (prayer) and the (next) prayer till he offers it.