With regard to someone who knows he has not performed a four rakʿah prayer but does not know whether it was ẓuhr or ʿishāʾ prayers, if he performs a four rakʿah prayer with the intention of making up the prayer that he did not perform, it is sufficient; moreover, he has the option of reciting Sūrat al-Ḥamd and the other surah aloud or in a whisper.