Narrated Ibn `Abbas: I brought water to `Uthman bin `Affan to perform the ablution while he was sitting on his seat. He performed the ablution in a perfect way and said, "I saw the Prophet performing the ablution in this place and he performed it in a perfect way and said, "Whoever performs the ablution as I have done this time and then proceeds to the mosque and offers a two-rak`at prayer and then sits there (waiting for the compulsory congregational prayers), then all his past sins will be forgiven." The Prophet further added, "Do not be conceited (thinking that your sins will be forgiven because of your prayer).

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: This verse is: "Verily, those who conceal the clear signs and the guidance which we have sent down...)" (2:159). I heard the Prophet 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.

Narrated Humran: (the freed slave of `Uthman bin `Affan) I saw `Uthman bin `Affan asking (for a tumbler of water) to perform ablution (and when it was brought) he poured water from it over his hands and washed them thrice and then put his right hand in the water container and rinsed his mouth and washed his nose by putting water in it and then blowing it out. Then he washed his face thrice and (then) forearms up to the elbows thrice, then passed his wet hands over his head and then washed each foot thrice. After that `Uthman said, "I saw the Prophet performing ablution like this of mine, and he 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. '