يَكْتُبُ — لَمْ يَكْتُبْ
Yaktubu is indicative. Lam makes yaktub jussive, shown by final sukūn. Lam is the governor; sukūn is the sign.
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What Jussive Means
The Jussive Imperfect: Governors, Conditions, and Request Responses
يَكْتُبُ — لَمْ يَكْتُبْ
Yaktubu is indicative. Lam makes yaktub jussive, shown by final sukūn. Lam is the governor; sukūn is the sign.