The great scholar Ibn al-Qayyim (may Allaah have mercy on him) wrote:
Sin may be more beneficial for a person – if it leads him to repent – than engaging in many acts of obedience. This is the meaning of the statement of one of the salaf,“‘A person may commit a sin and enter Paradise because of it, or he may do an act of worship and enter Hell because of it.’ They said, ‘How is that?’ He replied, ‘He may commit a sin and then it remains at the forefront of his thoughts, and when he stands or sits or walks he remembers his sin. So then there comes about shame, repentance, seeking forgiveness and regret, so that that will be the means of his salvation. And [on the other hand] one may perform a good deed and it remains at the forefront of his thoughts, so when he stands or sits or walks he always remembers it and it results in him being amazed [with himself] and prideful. So that will be from the cause of his doom.’”
So the sin may be the factor that leads him to obedience, good deeds and good conduct of the heart out of fear of Allah and shyness towards him, hanging his head in shame and weeping with regret, seeking the forgiveness of his Lord. Each of these effects is more beneficial for the slave than an act of obedience which results in him feeling powerful and proud or feeling contempt for people and and looking at them with belittlement. There is no doubt that this sin is better before Allah and is closer to safety and success than one who is amazed with his own acts of obedience and becomes haughty, and who thinks that he is doing Allah a favor. And even if he makes claims to the contrary, Allah is the Witness over what is in his heart. Such a person may feel enmity towards creation if they do not magnify him and humbled themselves before him, and he finds hatred in his heart for those who do not do so. And if he were to examine himself honestly, he would see that clearly.”
[Madaarij al-Saalikeen 1/299]
Research Center For Hadith 