From the work Al-Imâm Abu Abdillâh Shamsudeen Muhammad bn Muflih Al-Maqdisî Al-Hambalî [RahimahuLlaah]:
Chapter of Obligation of Repentance and Its Rulings
Repentance from sins is obligatory according to the text of the Sharî’ah; not according to the intellect as the Mu’tazilah say. One of them [incorrectly] did say: The matter is based on what the intellect sees as good or bad.
Every Muslim that has come of age is prone to sins. Some say the sin to repent from should not be a mere suspicion. [But] the author of Nihaayah al-Mub’tadi’oon wrote: The repentance from acts thought to be sins is acceptable. Some others say the sins must be ascertained.
However the most correct view is he who says: I repent to Allâh from such-and-such and I seek His forgiveness from it. The view that such repentance [in the former] is not acceptable is the one expressed by Al-Qaadee [Iyaad] – RahimahuLlaah – as a school of thought because repentance encompasses show of regret over what one had done of wrong. The regret is not seen as a condition because if it is so it becomes a naught.
Al-Qaadee said: When one is in doubts as to whether what he has done is evil or not such should see himself as being lax therefore he must repent from this lassitude. He should thereafter make effort to ascertain what is evil or good because whoever has come of age and is religiously culpable should not knowingly carry out evil acts, or acts that are not safe from being described as evil. Therefore if he knowingly goes ahead to carry out an act which he is not sure if it is not evil then he is lax and such an act of lassitude is itself a sin which he must repent from.
The basis for this matter is mentioned in the end of Chapter of Trust.
Ash-Shaykh Taqiyyudeen [Ibn Taymiyyah]s – RahimahuLlaah – said: Whoever generally repents from sins such an act of repentance will facilitate the forgiveness of all the sins except if there is a factor that comes to specifically limit this general sense of repentance [from the slave in question] such as when he fails to repent from some sins because of his special engrossment in them, or when he believes such acts are correct [whereas they are not], the result is that only some of his sins will be forgiven, according to the best view among the scholars.
[Al-Imaam] Muhydeen An-Nawawî – RahimahuLlaah – mentioned that the repentance will be held to have quashed the other sins. This is also what Al- – RahimahuLlaah – Qaatibee said to be the opposite of the view of the Mu’tazilah.
Ibn ‘Aqeel – RahimahuLlaah – said: What has been reported from Ahmad – RahimahuLlaah – is that repentance is not correct except when carried with respect to all sins. He was reported to have said about a man who said: If I am given lashes for Zinâ, I will not commit the act but I will not stop looking at women. Ahmad said: The lashes will not expiate his sin. Thus he [Al-Imâm Ahmad] said he would not be benefitted by shunning Zinâ while he still engages in the precursors of Zinâ such as looking at women.
Al-Aadaab Ash-Shar’iyyah p.70