Wa-yawmin introduces a day in a genitive poetic construction, often read with an implied rubba after the wāw. Ḥabastu is a past verb with first-person subject -tu, and al-nafsa is its direct object. The accusative verbal noun ḥifāẓan explains why the self was restrained and can be analyzed as a purpose accusative (mafʿūl li-ajlihi).
ʿAwrātihi here concerns the vulnerable points, exposed weaknesses, or honor needing protection in a group. Restricting it to the everyday anatomical meaning of ʿawrah would misread the military and social setting.