What does “al-ḥirṣ wa-ṭūl al-amal” explain?

Iṭnāb: Clarification after Ambiguity, Tawshīʿ, Repetition and Īghāl

• The two time references of yashīb and yashib
• Two governing elements of ibn Ādam
• Two levels of emphasis within ḥirṣ
• The dual khaṣlatān