Musnad Ahmad 1309:0

It was narrated from Maymunah bint Sa’d, the freed slave woman of the Messenger of Allah (ﷺ), that she said: "O Messenger of Allah, advise us regarding Bayt al-Maqdis (Jerusalem)." He said: "Go to it and pray in it." She said: "If one of us cannot go to it and pray in it?" He said: "Then send some oil to be used in its lamps, for whoever sends oil to it, it is as if he has prayed in it."