(the slave of 'Uthman) I saw 'Uthman bin 'Affan asking for a tumbler of water (and when it was brought) he poured water over his hands and washed them thrice and then put his right hand in the water container and rinsed his mouth, washed his nose by putting water in it and then blowing it out. then he washed his face and forearms up to the elbows thrice, passed his wet hands over his head and washed his feet up to the ankles thrice. Then he said, "Messenger of Allah ﷺ said 'If anyone performs ablution like that of mine and offers a two-rak'at prayer during which he does not think of anything else (not related to the present prayer) then his past sins will be forgiven.' "  

أَنَّهُ رَأَى عُثْمَانَ بْنَ عَفَّانَ دَعَا بِإِنَاءٍ فَأَفْرَغَ عَلَى كَفَّيْهِ ثَلاَثَ مِرَارٍ فَغَسَلَهُمَا ثُمَّ أَدْخَلَ يَمِينَهُ فِي الإِنَاءِ فَمَضْمَضَ وَاسْتَنْشَقَ ثُمَّ غَسَلَ وَجْهَهُ ثَلاَثًا وَيَدَيْهِ إِلَى الْمِرْفَقَيْنِ ثَلاَثَ مِرَارٍ ثُمَّ مَسَحَ بِرَأْسِهِ ثُمَّ غَسَلَ رِجْلَيْهِ ثَلاَثَ مِرَارٍ إِلَى الْكَعْبَيْنِ ثُمَّ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ مَنْ تَوَضَّأَ نَحْوَ وُضُوئِي هَذَا ثُمَّ صَلَّى رَكْعَتَيْنِ لاَ يُحَدِّثُ فِيهِمَا نَفْسَهُ غُفِرَ لَهُ مَا تَقَدَّمَ مِنْ ذَنْبِهِ  

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.  

أَلاَ أُحَدِّثُكُمْ حَدِيثًا لَوْلاَ آيَةٌ مَا حَدَّثْتُكُمُوهُ سَمِعْتُ النَّبِيَّ ﷺ 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}