“Those who fear their Lord unseen,” meaning: a man among them remembers his sin while in seclusion;
﴿الَّذين يَخْشونَ رَبهم بِالْغَيْبِ﴾ أَيْ: يَذْكَرُ الرَّجُلُ مِنْهُمْ ذَنْبَهُ فِي الْخَلَاءِ؛