لَمْ يَكْتُبْ — لَمَّا يَكْتُبْ
Both are jussive governors; lammā more strongly indicates “not yet,” usually with expectation that the act may occur.
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Lam versus Lammā: Meaning
The Jussive Imperfect: Governors, Conditions, and Request Responses
لَمْ يَكْتُبْ — لَمَّا يَكْتُبْ
Both are jussive governors; lammā more strongly indicates “not yet,” usually with expectation that the act may occur.