Musnad Abu Ya'la al-Mawsili 153:146

Nasr ibn Ali al-Jahdhami narrated to us, Abdullah—meaning Ibn Dawud—narrated to us, from Hanzalah ibn Abi Sufyan, from Salim, from Ibn Umar, from the Prophet (peace be upon him), who said: "Whoever keeps a dog, except for a hunting dog or a livestock dog, then two qirats from his reward decrease every day." Abu Hurayrah said: "Or a farm dog." He said: And Abu Hurayrah used to farm.