In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Allaah [The Most High] said:

وَٱلَّذِينَ إِذَا فَعَلُواْ فَـٰحِشَةً أَوۡ ظَلَمُوٓاْ أَنفُسَہُمۡ ذَكَرُواْ ٱللَّهَ فَٱسۡتَغۡفَرُواْ لِذُنُوبِهِمۡ وَمَن يَغۡفِرُ ٱلذُّنُوبَ إِلَّا ٱللَّهُ وَلَمۡ يُصِرُّواْ عَلَىٰ مَا فَعَلُواْ وَهُمۡ يَعۡلَمُونَ

And those who, when they have committed Faahisha [illegal sexual intercourse etc.] or wronged themselves with evil, remember Allaah and ask forgiveness for their sins; – and none can forgive sins but Allah – and do not persist in what they have done, while they know. [Soorah Aal Imraan’ Aayah 135]

[وَٱلَّذِينَ إِذَا فَعَلُواْ فَـٰحِشَةً أَوۡ ظَلَمُوٓاْ أَنفُسَہُمۡ ذَكَرُواْ ٱللَّهَ فَٱسۡتَغۡفَرُواْ لِذُنُوبِهِمۡ – And those who, when they have committed Faahishah (illegal sexual intercourse etc.) or wronged themselves with evil, remember Allah and ask forgiveness for their sins]- Meaning: When they commit sins, they return to Allaah in repentance and seek His protection from the evil consequences that might reach them in future due to their evil deeds and seek forgiveness for the evil deeds which they have already committed. [وَلَمۡ يُصِرُّواْ عَلَىٰ مَا فَعَلُواْ وَهُمۡ يَعۡلَمُونَ – And do not persist in what (wrong) they have done, while they know]- Meaning: They repent from their sin, turn to Allaah in repentance soon afterwards, refrain from persisting upon disobedience and they know that Allaah forgives whoever repents.

أُوْلَـٰٓٮِٕكَ جَزَآؤُهُم مَّغۡفِرَةٌ۬ مِّن رَّبِّهِمۡ وَجَنَّـٰتٌ۬ تَجۡرِى مِن تَحۡتِهَا ٱلۡأَنۡہَـٰرُ خَـٰلِدِينَ فِيہَا‌ۚ وَنِعۡمَ أَجۡرُ ٱلۡعَـٰمِلِينَ

For such, the reward is Forgiveness from their Lord, and Gardens with rivers flowing underneath (Paradise), wherein they shall abide forever. How excellent is this reward for the doers (who do righteous deeds according to Allah’s Orders). [Ref 1] And they know that persisting upon sin is harmful and abandoning it is a foremost obligation. [Ref 2]

When they commit evil deeds -be it major or minor- they hasten towards repentance, seek forgiveness, remember their Lord, the promise given to the disobedient ones and the promise given to those who fear Him, so they ask for forgiveness, ask Allaah to hide their faults, stop committing the sins and are regretful. And due to this, Allaah said about them: [ أُوْلَـٰٓٮِٕكَ جَزَآؤُهُم مَّغۡفِرَةٌ۬ مِّن رَّبِّهِمۡ وَجَنَّـٰتٌ۬ تَجۡرِى مِن تَحۡتِهَا ٱلۡأَنۡہَـٰرُ خَـٰلِدِينَ فِيہَا‌ۚ وَنِعۡمَ أَجۡرُ ٱلۡعَـٰمِلِينَ – For such, the reward is Forgiveness from their Lord, and Gardens with rivers flowing underneath (Paradise), wherein they shall abide forever. How excellent is this reward for the doers (who do righteous deeds according to Allah’s Orders)]. [Ref 3]

 Those Who Commit The Evil Act of Concealment, But Then They Repent, Do Righteous Deeds And Openly Declare What They Concealed

Allaah [The Most High] said:

إِنَّ ٱلَّذِينَ يَكۡتُمُونَ مَآ أَنزَلۡنَا مِنَ ٱلۡبَيِّنَـٰتِ وَٱلۡهُدَىٰ مِنۢ بَعۡدِ مَا بَيَّنَّـٰهُ لِلنَّاسِ فِى ٱلۡكِتَـٰبِ‌ۙ أُوْلَـٰٓٮِٕكَ يَلۡعَنُہُمُ ٱللَّهُ وَيَلۡعَنُہُمُ ٱللَّـٰعِنُونَ

إِلَّا ٱلَّذِينَ تَابُواْ وَأَصۡلَحُواْ وَبَيَّنُواْ فَأُوْلَـٰٓٮِٕكَ أَتُوبُ عَلَيۡہِمۡ‌ۚ وَأَنَا ٱلتَّوَّابُ ٱلرَّحِيمُ

Verily, those who conceal the clear proofs, evidences and the guidance, which We have sent down, after We have made it clear for the people in the Book, they are the ones cursed by Allah and cursed by the cursers. Except those who repent and do righteous deeds, and openly declare [the truth which they concealed]. These, I will accept their repentance. And I am the One Who accepts repentance, the Most Merciful. [Surah Al-Baqarah. Aayaat 159-160]

Abu Saaleh reported from Ibn Abbaas [radiyallaahu anhumaa] who said: This Aayah was revealed regarding the leaders of the Yahood, [who] concealed the Bayyinaat and the Hudaa, which Allaah revealed in the Tawraat. The Bayyinaat are the [rulings] regarding what is lawful and unlawful, the prescribed punishments and the obligatory [acts, duties]. And Hudaa [in this Aayah] is the description of the Prophet [sallal laahu alayhi wasallam] and his characteristics.  [أُوْلَـٰٓٮِٕكَ يَلۡعَنُہُمُ ٱللَّهُ وَيَلۡعَنُہُمُ ٱللَّـٰعِنُون- they (i.e. those who conceal the proofs) are the ones cursed by Allah and cursed by the cursers]. [إِلَّا ٱلَّذِينَ تَابُواْ وَأَصۡلَحُواْ وَبَيَّنُواْ فَأُوْلَـٰٓٮِٕكَ أَتُوبُ عَلَيۡہِمۡ‌ۚ وَأَنَا ٱلتَّوَّابُ ٱلرَّحِيمُ – Except those who repent and do righteous deeds, and openly declare (the truth which they concealed). These, I will accept their repentance. And I am the One Who accepts repentance, the Most Merciful]- Meaning: Ibn Mas’ood [radiyallaahu-anhu] said: Except those Yahood who repent, rectify their deeds and make known the characteristics of Allaah’s Messengers which are mentioned in their book. [Ref 4]

At-Tawbatun Nusooh- Sincere Repentance

Allaah [The Most High] said:

يَـٰٓأَيُّہَا ٱلَّذِينَ ءَامَنُواْ تُوبُوٓاْ إِلَى ٱللَّهِ تَوۡبَةً۬ نَّصُوحًا عَسَىٰ رَبُّكُمۡ أَن يُكَفِّرَ عَنكُمۡ سَيِّـَٔاتِكُمۡ وَيُدۡخِلَڪُمۡ جَنَّـٰتٍ۬ تَجۡرِى مِن تَحۡتِهَا ٱلۡأَنۡهَـٰرُ يَوۡمَ لَا يُخۡزِى ٱللَّهُ ٱلنَّبِىَّ وَٱلَّذِينَ ءَامَنُواْ مَعَهُ ۥ‌ۖ نُورُهُمۡ يَسۡعَىٰ بَيۡنَ أَيۡدِيہِمۡ وَبِأَيۡمَـٰنِہِمۡ يَقُولُونَ رَبَّنَآ أَتۡمِمۡ لَنَا نُورَنَا وَٱغۡفِرۡ لَنَآ‌ۖ إِنَّكَ عَلَىٰ ڪُلِّ شَىۡءٍ۬ قَدِيرٌ۬

O you who believe! Turn to Allah with sincere repentance! It may be that your Lord will remit from you your sins, and admit you into Gardens under which rivers flow [Paradise] the Day that Allah will not disgrace the Prophet [Muhammad] and those who believe with him, their Light will run forward before them and with [their Records Books of deeds] in their right hands they will say: ‘’Our Lord! Keep perfect our Light for us [and do not put it off till we cross over the Siraat (a slippery bridge over the Hell) safely] and grant us forgiveness. Verily, You are Able to do all things.’’

[يَـٰٓأَيُّہَا ٱلَّذِينَ ءَامَنُواْ تُوبُوٓاْ إِلَى ٱللَّهِ تَوۡبَةً۬ نَّصُوحًا – O you who believe! Turn to Allah with sincere repentance]- Meaning: Umar Ibn Khattaab [radiyallaahu anhu] said: ‘’At-tawbatun Nosooh [sincere repentance] is that a person repents from sins and reminds himself not to return to sinning. Al-Hasan Al-Basri [rahimahullaah] was asked about At-tawbatun Nusooh [sincere repentance], so he said: ‘’It is regret [felt in] the heart, asking for forgiveness with the tongue, the limbs refrain from sinning and being careful of returning to sinning. Ibn Mas’ood [radiyallaahu-anhu] said: ‘’At-tawbatun Nusooh [sincere repentance] expiates every evil deed’’, then he recited the Aayah the Aayah [i.e. Aayah 8 Surah At-Tahreem] [Ref 5]

Shaqeeq Al-Balkhiy (rahimahullaah) said: ‘’The signs of repentance are: Weeping over what has preceded [of sins]; fear of falling into sin; keeping way from evil companions and accompanying the good people. [Ref 6]

The Hypocrites Will Be In The Depths of The Fire, Unless They Repent Before Death

Allaah [The Most High] said:

إِنَّ ٱلۡمُنَـٰفِقِينَ فِى ٱلدَّرۡكِ ٱلۡأَسۡفَلِ مِنَ ٱلنَّارِ وَلَن تَجِدَ لَهُمۡ نَصِيرًا

إِلَّا ٱلَّذِينَ تَابُواْ وَأَصۡلَحُواْ وَٱعۡتَصَمُواْ بِٱللَّهِ وَأَخۡلَصُواْ دِينَهُمۡ لِلَّهِ فَأُوْلَـٰٓٮِٕكَ مَعَ ٱلۡمُؤۡمِنِينَ‌ۖ وَسَوۡفَ يُؤۡتِ ٱللَّهُ ٱلۡمُؤۡمِنِينَ أَجۡرًا عَظِيمً۬ا

مَّا يَفۡعَلُ ٱللَّهُ بِعَذَابِڪُمۡ إِن شَكَرۡتُمۡ وَءَامَنتُمۡ‌ۚ وَكَانَ ٱللَّهُ شَاڪِرًا عَلِيمً۬ا

Verily, the hyprocrites will be in the lowest depths of the Fire and no helper will you find for them; except those who repent, act righteously, hold fast to Allaah and purify their religion for the sake of Allaah, then they will be with the believers. And Allah will grant to the believers a great reward. Why should Allah punish you if you have thanked [Him] and have believed in Him. And Allah is Ever All-Appreciative [of good], All-Knowing. [Surah An-Nisaa. Aayaat 145-147]

[إِلَّا ٱلَّذِينَ تَابُواْ  – Except those who repent]- Meaning: Except those who repent from hypocrisy; [وَأَصۡلَحُواْ  – and act righteously]- Meaning: Rectify their deeds after repenting;  [وَٱعۡتَصَمُواْ – hold fast to Allaah]- Meaning: Adhere to the religion ordained by Allaah; [وَأَخۡلَصُواْ دِينَهُمۡ لِلَّهِ- and purify their religion for the sake of Allaah]- Meaning: The religion of Islaam- sincerely adhere to it and keep away from shirk; act sincerely and removed from the filthy [acts and beliefs that are tantamount to] Nifaaq [hypocrisy] and Riyaa [showing off]. [فَأُوْلَـٰٓٮِٕكَ مَعَ ٱلۡمُؤۡمِنِينَ‌ۖ وَسَوۡفَ يُؤۡتِ ٱللَّهُ ٱلۡمُؤۡمِنِينَ أَجۡرًا عَظِيمً۬ا – then they will be with the believers. And Allah will grant to the believers a great reward].

[مَّا يَفۡعَلُ ٱللَّهُ بِعَذَابِڪُمۡ إِن شَكَرۡتُمۡ وَءَامَنتُمۡ‌ۚ وَكَانَ ٱللَّهُ شَاڪِرًا عَلِيمً۬ا – Why should Allah punish you if you have thanked (Him) and have believed in Him. And Allah is Ever All-Appreciative (of good), All-Knowing]. [Ref 7]

[Ref 1: An Excerpt from ‘Al-Misbaah Al-Muneer Fee Tahdheeb Tafseer Ibn Katheer’. Slightly paraphrased]; [Ref 2: An Excerpt from ‘Zaadul Maseer Fee Ilmit Tafseer’. Slightly paraphrased]; [Ref 3: An Excerpt from ‘Tayseer al-Kareem Ar-Rahmaan Fee Tafseer Kalaam al-Mannaan’. Slightly paraphrased]; [Ref 4]: An Excerpt from ‘Zaadul Maseer An Ilmit Tafseer’. Slightly paraphrased]; [Ref 5: An Excerpt from ‘Zaadul Maseer Fee Ilmit Tafseer’. By Imaam Ibnul Jawzi (rahimahullaah)]; [Ref 6: Nazhatul Fudalaa 711]; [Ref 7: An Excerpt from Zaadul Maseer Fee Ilmit Tafseer’ by Imaam Ibnul Jawzi (rahimahullaah). Slightly paraphrased]