How does fa-nṣab function in fa-idhā faraghta fa-nṣab?

Supplementary Practice 18: Rhetorical Analysis of Sūrat al-Ḍuḥā and Sūrat al-Sharḥ

• A passive past verb negating the earlier verb
• A delayed noun of inna
• The subject inside a relative clause
• An imperative introduced by fā in a conditional temporal context