Is it permissible to greet the dead from behind a veil or a wall, and does it reach them?

The scholars have not established a statement that stipulates for visiting graves and supplicating for their occupants that it must be done directly upon seeing them, or that the visitor must be inside the enclosure. Sheikh Ibn Uthaymeen holds that greeting the occupants of graves from outside the enclosure is possibly permissible. The apparent meaning of the Ahadith indicates that the dead hear and comprehend the greetings, as happened with the slain at Badr and with the deceased hearing the footsteps of those accompanying the funeral.