Fiqh-Us-Sunnah, Vol 2, #34.
Abu Bakr (r) reports: “I heard the Prophet sallallahu alehi wasallam saying:
‘Allah forgives the man who commits a sin (then feels ashamed), purifies
himself, offers a prayer and seeks His forgiveness.’ Then he recited the
‘ayyah: ‘And those who, when they do an evil thing or wrong themselves,
remember Allah and implore forgiveness for their sins – and who can forgive
sins except Allah? – and will not knowingly repeat (the wrong) they did. The
reward of such will be forgiveness from their Lord, and gardens underneath
which rivers flow, wherein they will abide forever- a bountiful reward for
workers.”‘ [al-'lmran: 135-136]. This is related by Abu Dawud, an-Nasa’i, Ibn
Majah, al-Baihaqi, and at-Tirmidhi who calls it hasan.
At-Tabarani records in al-Mu’jam al-Kabir, with a hasan chain, from Abu
ad-Darda’ that the Prophet sallallahu alehi wasallam said: “Whoever makes
wudu’ and perfects the wudu’ and then stands and prays two rak’at or four
rak’at, obligatory or non-obligatory, and perfects therein his ruku’ and sujjud
and then asks for Allah’s forgiveness, he will be forgiven.“