God says
Say: “[Thus speaks God:] ‘O you servants of Mine who have transgressed against your own selves! Despair not of God’s mercy : behold, God forgives all sins*-- for, verily, He alone is much-forgiving, a most gracious!’” -- Q.39: 53 *
“whenever the sinner repents and turns to Him”
They who bear the throne of [God’s] almightiness, as well as all who are near it, extol their Sustainer’s limitless glory and praise, and have faith in Him, and ask forgiveness for all [others] who have attained to faith: “O our Sustainer! Thou embracest all things within [Thy] grace and knowledge: forgive, then, their sins unto those who repent and follow Thy path, and preserve them from the blazing fire! And O our Sustainer, bring them into the garden of perpetual bliss, then, which Thou hast promised them, together with their spouses and their offspring – for, verily, Thou alone art almighty, truly wise – and preserve Thou wilt have preserved from [the taint of] evil deeds, him wilt Thou have graced with Thy mercy: and that, that will be the triumph supreme!” -- Q.40: 7-9
O you have attained to faith! Turn unto God in sincere repentance. …. Q.66: 8
Prophet said
1. “Whoever sticks to seeking forgiveness, God creates for him a way out of every difficulty and a relief from every anxiety, and supplies provision from where he cannot think of…” – H: Ahmed, Abu Daud and Ibn Majah. N: Ibn Abbas.
2. “Verily the gift of the living to the dead is seeking forgiveness for them” --H: Baihaqi. N: Abdullah-b-Abbas.
Following are a few supplications:
1. Rabbana faghfir lana zunubana wa kaffir unna saiy-ye aatina wa tawaffana ma al abraar. (3: 193) (…. O our Sustainer! Forgive us, then, our sins, and efface our bad deeds; and let us die the death of the truly virtuous!)
2. Rabbana zalamna unfusana wa inlam taghfir lana wa tarhamna lanakoo-nanna minal khaasireen (7: 23). (O our Sustainer! We have sinned against ourselves – and unless Thou grant us forgiveness and bestow Thy mercy upon us, we shall most certainly be lost!)Prayer of Adam and Eve: repentance for a sin that is realized and can recur.
3. Rabbanagh-firlee waliwalidayya walilmumineena yawma yaqoomul-hisaab (14: 41)(Grant Thy forgiveness unto me, and my parents, and all the believers, on the Day on which the [last] reckoning will come to pass.)
4. Rabigh-fir warham wa anta khairur-raahemeen (23: 118) (O my Sustainer! Grant [me] forgiveness and bestow Thy mercy [upon me]: for Thou art the truest bestower of mercy!)
4. Rabigh-fir warham wa anta khairur-raahemeen (23: 118) (O my Sustainer! Grant [me] forgiveness and bestow Thy mercy [upon me]: for Thou art the truest bestower of mercy!)