Concept:Visiting the Prophet's mosque in Madinah is a recommended act of worship, not an obligation or invalidator.
Explanation:The Prophet (S.A.W) encouraged visiting his mosque in Madinah.
This visit is rewardable and considered praiseworthy.
It may be done before or after performing Hajj.
In Islamic jurisprudence, such a recommended action is called
Mandub.
It is not Makruh (disliked), Mubah (merely permissible), or Mubatilat (invalidator).
Therefore, the correct ruling is Mandub.
Answer:B. Mandub