What is the ruling on selling electrical tools (wires and plastic) to a mosque that contains a shrine, separated by a wall? And what is due upon one to do regarding this buyer?

If the purchaser of the goods intends to illuminate a shrine, whether inside or outside a mosque, it is not permissible to sell these goods to him or assist him in any way, based on Allah's saying: (And cooperate in righteousness and piety, but do not cooperate in sin and aggression). Lighting lamps on graves is a forbidden innovation, and scholars have stipulated its prohibition because it is extravagance and an imitation of the Majus (Zoroastrians).

If the shrine is inside the mosque, it is not permissible to combine a mosque and a grave in Islam. If the grave predates the mosque, the mosque must be demolished or abandoned. If the mosque predates, the grave must be exhumed and the deceased removed from it. In both cases, it is not permissible to assist anyone who wishes to install these items, as it constitutes an affirmation of a reprehensible act.

However, if the shrine is next to the mosque and separated by a wall, there is no harm, and the mosque is considered like other mosques of the Muslims.