Shaykh al-Islam Ibn Taymiyyah رحمه الله said,
"With regards to the question, 'Does the mere acknowledgement of sin combined with tawheed lead to its forgiveness and the alleviation of difficulty, or is something else required?' we answer by saying:
What lead to forgiveness of sins, along with tawheed, is repentance. [1] For example, Allaah سبحانه و تعالى will not forgive shirk unless it be repented from, as He, the Exalted, says in two places in the Qur'an,
"Indeed, Allaah forgives not that partners should be set up with him in worship, but He forgives what is less than that for whom He wills. And whoever sets up partners with Allaah in worship, he has indeed invented a tremendous sin." (4:48)
" Verily! Allaah forgives not (the sin of) setting up partners in worship with Him, but He forgives what is less than that for whom He wills. And whoever sets up partners in worship with Allaah, has indeed strayed far away." (4:116)
Any sin other than shirk is forgiven if repented from, but if not, it is up to Allaah سبحانه و تعالى. If He wishes, He will forgive it, and if He wishes, He will not. Allaah, the Exalted, says:
"Say, "O My servants who have transgressed against themselves (by committing evil deeds and sins)! Despair not of the Mercy of Allaah, verily Allaah forgives all sins. Truly, He is Oft-Forgiving, Most Merciful." (39:53)
This verse concerns the penitent, and this is why the verse has been generalised and left unrestricted, and it has been decisively stated that He forgives all sins. In the previous verses, however, He says:
"Indeed, Allaah forgives not that partners should be set up with him in worship, but He forgives what is less than that for whom He wills. And whoever sets up partners with Allaah in worship, he has indeed invented a tremendous sin." (4:48)
" Verily! Allaah forgives not (the sin of) setting up partners in worship with Him, but He forgives what is less than that for whom He wills. And whoever sets up partners in worship with Allaah, has indeed strayed far away." (4:116)
specifying the forgiveness of all sins other than shirk to be dependant upon His will. Now if Allaah سبحانه و تعالى will only forgive shirk for the one who asks forgivness, and He will forgive any other sin that person repents from, the only meaning left for this verse is that those sins, other than shirk, that are not repented from, Allaah سبحانه و تعالى will forgive them, or not forgive them, as He wills.
Acknowledgement of sin, if it includes repentance, combined with tawheed, leads to forgiveness. When sin is forgiven, its punishment is averted, for forgiveness is a shield, protecting one from the evil of that sin.
Some people say that al-ghafr (forgiveness) means as-satar (covering), reasoning that maghfirah (forgiveness) and al-Ghaffaar (the Oft-Forgiving) were only called so because of the meaning they carry of covering and hiding. They also explain the meaning of His Name, al-Ghaffaar to be as-Sattaar (the Coverer). This is an incomplete explanation of al-ghafr. The meaning of forgiveness is to shield oneself from the evil of sin such that he not be punished for it. Hence, the one who is forgiven is not punished for that sin. The meaning of covering does not imply this meaning, for the one whose sin has been hidden could still be punished for it in private. [2]
However, despite having repented, a person could still be tried with something that would serve to increase his reward, and this does not negate the reality of forgiveness.
Moreover, a person could think another to have repented of sin, but in reality he is merely someone who has abandoned that sin. The one who abandons is not the same as the one who has repented. A person may not commit a sin because it never occured to him to do so, or because he was unable to, or his desire to commit it left him for other than a religious one, all of these reasons do not constitute repentance. It is necessary that the penitent believe that what he did was evil, that he hate that deed simply because Allaah سبحانه و تعالى prohibited it, and that he leave it for the sake of Allaah سبحانه و تعالى and not for some worldly desire or fear. Repentance is from the greatest of good deeds, and all good deeds can only be considered to be so if they are performed for the sake of Allaah سبحانه و تعالى and in accordance to His command. Concerning the verse:
"Who has created death and life, that He may test you which of you is best in deed. And He is the All-Mighty, the Oft-Forgiving." (67:2)
Fudayl Ibn 'Iyaad رحمه الله said, 'The sincere and correct.' When asked what that means he replied, 'When an action is sincere but not correct, it will not be accepted. When it is correct but not sincere, it will not be accepted. It will only be accepted when it is both sincere and correct; sincere, meaning that it be only for Allaah سبحانه و تعالى; and correct, meaning that it be performed in the way taught by the Prophet Muhammad صلى الله عليه وسلم [the Sunnah].' [3]
Sayyiduna 'Umar Ibn al-Khattaab رضي الله عنه would say in his supplication, 'O Allaah! Make all of my deeds righteous, make them sincerely for Your Face, and do not let any portion of them be for anyone else.' [4]
As for acknowledging ones sin, in submissiveness to Allaah سبحانه و تعالى, but without the intent to abandon it, then this is merely asking for forgiveness and cannot be said to be repentence. This like a person who asks of Allaah سبحانه و تعالى to forgive his sin but has not repented from it. One cannot be certain of his forgiveness, for he is in the position of one who is making a mere supplication. It is established that the Prophet صلى الله عليه وسلم said, 'There is no supplicant who supplicates for something that does not contain any sin or the severing of kindred-relations, except that one of three things will occur; either it is answered in this life; or he gets the likes of it in reward; or its equivalent in evil is averted from him.' He was asked, 'O Messenger of Allaah! What if we frequently supplicate?' He replied, 'Allaah increases.' [5]
The likes of this supplication could lead to forgiveness and if not, the attainment of some other good or the aversion of some evil. Hence, in all cases it brings about benefit and this is true of all supplications.
Those amongst the scholars who said, 'Asking for forgiveness while persisting in that sin is the repentance of liars' meant one who claims to have repented. If such a person persists in the sin then it becomes clear that he has not in reality repented, for repentance and persistence in sin are two opposites. Persistence in sin opposes repentence, but it does not oppose the mere asking for forgiveness when divorced from repentance." [6]
Notes:
[1] The conditions for repentance are as follows: sincerity, feeling remorse for that sin, repenting, and not persisting in the sin. Allaah سبحانه و تعالى says:
"And those who, when they commit an immorality or wrong themselves [by transgression], remember Allah and ask forgiveness for their sins; - and none can forgive sins but Allah - And do not persist in what (wrong) they have done, while they know. 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)." (3:135-136)
Moreover, repenting before it is too late, i.e. before the final throes of death or before the sun rises from the west.
[2] Refer to al-Mufradat p362; Lisan al-'Arab 5/25; Mu'jam Maqayis al-Lugha 4/385.
[3] Tafseer al-Baghawi.
[4] Imam Ahmad رحمه الله in az-Zuhd #615 on the authority of al-Hasan رحمه الله from Sayyiduna 'Umar رضي الله عنه. Al-Hasan رحمه الله was not contemporary to Sayyiduna 'Umar (may Allaah be pleased with him).
[5] Al-Maqdisi, Targheeb ad-Du'a #21 on the authority of Sayyiduna Anas. Similar Ahaadeeth are also reported on the authority of Sayyiduna Abu Sa'eed al-Khudri رضي الله عنه by Imam Ahmad [#11133] رحمه الله, Sayyiduna 'Ubadah Ibn as-Saamit رضي الله عنه by at-Tirmidhi [#3573] رحمه الله and Sayyiduna Abu Hurayrah رضي الله عنه by Imam Ahmad رحمه الله. At-Tirmidhi رحمه الله said that it was hasan saheeh, al-Haakim رحمه الله said that is was saheeh and Imam adh-Dhahabi رحمه الله agreed as did Shaykh al-Albani رحمه الله, Saheeh at-Targheeb #1631/
[6] Relief From Distress: An Explanation To The Du'a Of Yunus عليه السلام, pp 163-168
See also:
Tawbah (Repentance) - http://www.muftisays.com/forums/53-duaas--supplications/5476-tawbah-repentance.html
Foregive Me For I Have Sinned - http://www.muftisays.com/forums/12-virtues/5116-forgive-me-for-i-have-sinned.html