Continuation of the explanation of Ibn Malik’s (may Allah have mercy on him) saying: “And you lighten it if the action is omitted *** and the lam is obligatory if it is neglected.”

The Shaykh : Because it distinguishes between the negating *in* and the lightened *in*. Then, is it the *lam* of the beginning or the *lam* of *jidd*? There is a disagreement on this that does not matter; nothing is written.
Now, is the *lam* obligatory if it is neglected and if it is made active?
The student: It is not obligatory.

The Shaykh : It is not obligatory. Why? Because there is no ambiguity between it and the negating *in*.