Musnad Abu Ya'la al-Mawsili 155:221

Suwayd ibn Sa'id narrated to us, Ziyad ibn al-Rabi' al-Yahmadi narrated to us, from Hisham, from Muhammad ibn Sirin, from Abu Hurayrah, who said: The Prophet (peace be upon him) said: "The mouse is a transformed creature (maskh), and the sign of that is that it drinks the milk of sheep but does not drink the milk of camels."