Musannaf Ibn Abi Shayba 3:5214

Abu Mu'awiyah narrated to us, from al-A'mash, from Ibrahim, from al-Aswad and Alqama, they said: Abdullah said: "There will be rulers over you who will delay the prayer from its time and stifle it until the death of the dead. So when you see them doing that, pray in your houses, then make your prayer a voluntary one (nafilah)."