Is repentance and seeking forgiveness permissible for unknown sins, and what is meant by the the Prophet's (peace be upon him) saying: "And I seek Your forgiveness for what I do not know"?

The abundance of sins that a person may not even be aware of necessitates a general repentance, comprehensive of all sins, known and unknown. Repentance is always obligatory because a person either falls short in what is commanded or transgresses what is forbidden. One seeks forgiveness for what they do not perceive as a sin, or for what they have forgotten. Concluding good deeds with seeking forgiveness, and the supplication "and I seek Your forgiveness for what You know," encompasses all sins, including those the servant is unaware of, such as hidden shirk, and what the servant forgets, and Allah alone knows them all.