Parsing the phrase: "The prayer is congregational"

Question:
Why is "the congregational prayer" in the accusative case?

Answer:
It is in the accusative case due to an implied verb, or what they call "al-ighra'" (incitement). They call this construction "al-ighra'." There is a chapter in grammar books called the Chapter of Al-Ighra'. For example, "The lion, the lion" — if you want to warn someone, "The viper, the viper" is in the accusative case due to al-ighra', meaning "Beware of the viper," or "Beware of the lion," or "Beware of the enemy." Here, the intended meaning is the prayer, i.e., "Attend it." Al-Ighra' is incitement to attend the prayer, specifically the eclipse prayer. "The prayer is congregational" means "Attend it." The word "salah" (prayer) is in the accusative case as the object of an implied verb, which is "Attend." The sign of its accusative case is the fathah. "Jami'ah" (congregational) is in the accusative case as a state (hal) describing the prayer, and the state is always in the accusative case. The sign of its accusative case is the visible fathah. This is the reason for the accusative case. Yes, it falls under the category of al-ighra'. Al-Ighra' means encouraging attendance and urging attendance. This is the meaning of al-ighra': urging someone to do something, or urging them to avoid something and beware of it. Yes.