Musannaf Ibn Abi Shayba 37:336

Hussain bin Ali narrated to us, from Za'idah, from Abd al-Malik bin Umayr, from Sa'id bin Amr bin Sa'id, from Abu Hurayrah, who said: "Not much time will pass for you until the fox fulfills its sunnah between two of the pillars of the mosque." Abd al-Malik said: "It is the mosque of Medina," meaning [due to] the ruin.