What is the contextual force of lā in “sa-nuqriʾuka fa-lā tansā”?

Supplementary Practice 28 — Comparative Rhetoric of Sūrat al-Aʿlā and Sūrat al-Ghāshiyah

• Prohibitive lā forbidding forgetfulness
• A semantically empty linking lā
• Negation within an assurance
• Lā negating the genus