Musnad Abu Ya'la al-Mawsili 188:1

Abu Talib Abd al-Jabbar ibn Asim narrated to us, Ismail ibn Ayyash narrated to us, from Thabit ibn al-Ajlan al-Ansari, that Abu Kathir al-Muharibi narrated to him, that Kharasha narrated to him, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Verily, there will be tribulations after me. The one who is asleep during them is better than the one who is awake, and the one who is sitting during them is better than the one who is standing, and the one who is standing during them is better than the one who is walking. So whoever encounters them, let him take his sword, then let him walk to a smooth rock and strike it with it until it breaks. Then let him lie down for it until it clears up, upon whatever it clears up."