«وَلَا تَمْنُنْ تَسْتَكْثِرُ»
Do not confer a favour seeking to gain more.
The source discusses the role of tastakthiru within the grammatical treatment of an affirmative imperfect linked to the governing utterance. The affirmative imperfect (المضارع المثبت) naturally carries present or unfolding force, so circumstantial wāw cannot simply be inserted without regard to the construction.
Example: “Jāʾa Zaydun yaḍḥaku” — Zayd arrived laughing. The implied subject of “yaḍḥaku” refers to Zayd, and the imperfect verb describes a concurrent action. One should not treat “Jāʾa Zaydun wa-yaḍḥaku” as an interchangeable default circumstantial form.