حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنِ الأَعْمَشِ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي هُرَيْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ إِنَّ أَحَدَكُمْ إِذَا تَوَضَّأَ فَأَحْسَنَ الْوُضُوءَ ثُمَّ أَتَى الْمَسْجِدَ لاَ يَنْهَزُهُ إِلاَّ الصَّلاَةُ لَمْ يَخْطُ خَطْوَةً إِلاَّ رَفَعَهُ اللَّهُ عَزَّ وَجَلَّ بِهَا دَرَجَةً وَحَطَّ عَنْهُ بِهَا خَطِيئَةً حَتَّى يَدْخُلَ الْمَسْجِدَ ‏"‏ ‏.‏

Humran the freed slave of 'Uthman bin 'Affan said

"I saw 'Uthman bin 'Affan sitting in Maqa'id. He called for water and he performed ablution, the he said: 'I saw the Messenger of Allah sitting in this place where I am sitting, performing ablution as I have done. Then he said: "Whoever performs ablution as I have done, his previous sins will be forgiven." And the Messenger of Allah said: "And do not be conceited (due to this great virtue)." (Sahih)Another chain with similar wording.