What is the ruling on visiting the household of the Prophet, peace and blessings be upon him, and is it obligatory? What are its conditions if it is permissible, or the reason for its prohibition if it is impermissible?

Visiting living relatives (Ahl al-Bayt) is permissible so long as it does not involve anything prohibited, and it is recommendable if it is for a sick person or out of love for the sake of Allah. This is based on the Prophet's (peace and blessings be upon him) saying: "A man went to visit a brother of his in another village. Allah appointed an angel to wait for him on his way. When he came to him, the angel asked, 'Where are you going?' He said, 'I am going to visit a brother of mine in this village.' The angel asked, 'Do you owe him any favor that you are looking after?' He said, 'No, other than that I love him for the sake of Allah, the Mighty and Majestic.' The angel said, 'Indeed, I am a messenger from Allah to inform you that Allah has loved you as you have loved him for His sake.'"