Continuation of the explanation of the verse: If you seek aid, the name of the one called is in the genitive case *** with the lam open, like "ya" for al-Murtada.

The Shaykh : If we make it a case of seeking aid, we say: "Ya la-Zayd." "Ya" is the particle of seeking aid, and "lam" is a preposition. "Zayd" is the one being sought aid from, and it is in the accusative case. Is it built on a hidden dammah at its end? We say: It is in the accusative case with a hidden fathah at its end, the appearance of which is prevented because the position is occupied by the movement of the preposition. Yes, and it is "Zayd" to clarify that he is the one being sought aid from. Now, the author says:
"like 'ya' for al-Murtada":
And what is the original form: "Ya al-Murtada" without seeking aid? "Ya al-Murtada": Its original form without seeking aid is: "Ya Murtada," here, yes, or: "Ya ayyuha al-Murtada," if we keep the article.