We are forewarned against dogs in…
Kesef Mishna which brings the Gemora supporting the Rambam in Mesechtes Bava Kama 15:2 not to have a dog in your house.
and Rambam Hilchos Talmud Torah 6:14, and Hilchos Nizkei Mamon 5:9, Chazon Ish on Choshen Mishpat Likutim 18:9.