Allaah – the Might and Majestic – says: “Say O My Slaves who have transgressed against their own souls! Do not despair of Allaah’s mercy. Indeed Allaah forgives all sins, Truly He is Oft-Forgiving, Most Merciful.” [Soorah az-Zumar 39:53].
There is a consensus from the Scholars that this noble aayah (verse) was revealed for the taa’ibeen (those who repent). So whoever sincerely repents from his sins, then Allaah will forgive him all his sins, as occurs in the saving of Allaah – the Most Perfect – :
“O you who Believe! Turn to Allaah in sincere repentance. Perhaps your Lord may remove from you your sins and admit you into Paradise beneath which rivers flow.” [Soorah at-Tahreem 66:8].
So in this aayah (verse), Allaah has made the removal of sins and entry into Paradise dependant upon sincere repentance.
And sincere repentance is conditional upon:
[i] abandoning the sin and keeping away from it,
[ii] having regret and remorse for committing the sin,
[iii] truly intending not to commit the sin again,
[iv] remembering the greatness of Allaah and hoping for His reward, whilst fearing His punishment.
“Turn you all in repentance to Allaah, O Believers, in order that you may be successful.” [Soorah an-Noor 24:31].
in this aayah (verse) Allaah the Mighty and Majestic – linked success with tawbah (repentance) and points to the fact that the repentant person will reach success and happiness, and if such a person were to follow up this repentance with eemaan (faith) and doing righteous actions, then Allaah would efface his evil actions and change them to good actions, as Allaah the Most Perfect – said after mentioning the sins of Shirk (directing worship that is due only for Allaah to other than Allaah), taking a life without just cause and fornication and adultery
“And whoever does this, will receive the punishment, The punishment will be doubled for him on the Day of Judgement and he will live therein in disgrace. Except for those who repent, have eemaan (faith) and do righteous actions. For them Allaah will change their evil deeds into good ones, and Allaah is Oft-Forgiving, Most Merciful.” [Soorah al-Furqaan 25:68-70]
And from the causes of tawbah (repentance) are humility and submissiveness to Allaah – the Most Perfect – and asking Allaah for guidance and ability, and that acceptance of one’s repentance is considered as a Favour from Allaah, as Allaah – the Most Perfect – said:
‘‘Call upon Me and I will respond to your supplication.” [Soorah Ghaafir 40:60] And He – the Mighty and Majestic – said: “And when My servant asks you concerning Me, say to them that I am indeed near, And I respond to the supplication of the one who supplicates to Me.” [Soorah al-Baqarah 2:186].
Also, from the causes of tawbah is choosing good companionship and friendship and following them in righteous conduct, whilst staying clear of bad companionship. It is authentically related from Allaah’s Messenger sallaallaahu ‘alayhi wa sallam that he said:
“A person is upon the way of life of his friend, so let one of you look to whom he keeps as a friend.”2 And the Prophet sallaallaahu ‘alayhi wa sallam also said: “The example of a good companion and a bad companion is like that of a seller of musk, and the one who blows the blacksmith’s bellows. As for the seller of musk, then either he will grant you some, or at the very least you enjoy a pleasant smell from him. As for the one who blows the blacksmith’s bellows, then either he will burn your clothes or you will get an offensive smell from him.”3
1. Al-Fataawaa (1/251-253)
2. Hasan: Related by Abu Dawood (no.4812) and others, from Abu Hurayrah radiallaahu ‘anhu. Imaam an-Nawawee authenticated it in Riyaadus-Saaliheen (no.174).
3. Related by al-Bukhaaree (4/323) and Muslim (no.2628), from Abu Moosaa al-Asharee radiallaahu ‘anhu.
Everything is for Allah's sake 