Musnad Ahmad 30:2452

Yahya narrated to us, from Ibn Abi Dhi'b, who said: Sa'id and Hajjaj narrated to me, they said: Layth narrated to us, he said: Sa'id narrated to me, from his father, from Abu Hurairah, from the Prophet (peace and blessings of Allah be upon him), who said: "O Muslim women," (Yahya said: He said it three times), "let no neighbor belittle her neighbor, even if it be the hoof of a sheep."