In the Qur’an, Allah reveals:
If Allah were to punish people for their wrong actions, not a single creature would be left upon the earth, but He defers them till a predetermined time. When their specified time arrives, they cannot delay it for a single hour nor can they bring it forward. (Surat an-Nahl; 61)
If Allah were to punish people during this life for their wrong actions, no being, without exception, would be left upon the Earth. Obviously, believers are included in this. Therefore, no believer can see himself as sinless and without error.
Knowingly or not, believers commit various sins throughout the course of their lives. The number of these sins or mistakes varies according to one's wisdom, consciousness and the profoundness of one’s faith. No one can regard himself as sinless—for doing so is a serious mistake. We learn from the Qur’an that claiming to be without error was an attribute of Pharaoh’s perverted character.
As the faith of a Muslim becomes firmer and he grows wiser, he begins to better recognize his sins and mistakes. Attaining a better awareness of his situation and a deeper fear of Allah leads him to a more serious effort to correct himself and seek forgiveness for the sins he committed intentionally or unintentionally. This is the practice of a conscientious Muslim. As a matter of fact, asking for forgiveness is an obligation for believers:
Ask your Lord for forgiveness and then repent to Him. He will let you enjoy a good life until a specified time, and will give His favor to all who merit it. But if you turn your backs, I fear for you the punishment of a Mighty Day. (Surah Hud; 3)
We may see that such obedience in asking Allah for forgiveness will be a means to His favors. Throughout the Qur’an, there are references to prophets asking forgiveness for various reasons. Although they were protected from committing sin, they would still ask for forgiveness when faced with a test or when they merely remembered Allah’s punishment. Allah considers asking for forgiveness a praiseworthy practice of believers:
And they would seek forgiveness before the dawn. (Surat adh-Dhariyat; 18)
As you can see, it is not essential to commit a mistake in order to ask for forgiveness from Allah. Asking for forgiveness is, in a way, expressing one’s weakness and insignificance in the shadow of Allah’s infinite might and recognizing the fact that it is impossible to avoid sins without His help.
Being unaware of one’s mistakes and sins—that is, a state of heedlessness and unconsciousness—prevents one from seeking forgiveness. As a consequence, one’s heart hardens, and a person can ultimately become arrogant and deem himself perfect, thus attributing to himself a quality equal with Allah (Allah is surely beyond that).