Sahih Muslim Book - 2, Hadith - 548

حَدَّثَنَا هَارُونُ بْنُ سَعِيدٍ الْأَيْلِيُّ حَدَّثَنَا ابْنُ وَهْبٍ قَالَ وَأَخْبَرَنِي مَخْرَمَةُ بْنُ بُكَيْرٍ عَنْ أَبِيهِ عَنْ حُمْرَانَ مَوْلَى عُثْمَانَ قَالَ تَوَضَّأَ عُثْمَانُ بْنُ عَفَّانَ يَوْمًا وُضُوءًا حَسَنًا ثُمَّ قَالَ رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ تَوَضَّأَ فَأَحْسَنَ الْوُضُوءَ ثُمَّ قَالَ مَنْ تَوَضَّأَ هَكَذَا ثُمَّ خَرَجَ إِلَى الْمَسْجِدِ لَا يَنْهَزُهُ إِلَّا الصَّلَاةُ غُفِرَ لَهُ مَا خَلَا مِنْ ذَنْبِهِ.

It was narrated that Humran, the freed slave of 'Uthman, said: "'Uthman bin 'Affan performed Wudu' one day and performed Wudu' well, then he said: 'I saw the Messenger of Allah (s.a.w) performing Wudu' and doing it well, then he said: "Whoever performs Wudu' like this, then goes out to the Masjid with no motive other than the prayer, his previous sins will be forgiven."