Musnad Ahmad 30:3272

Hajjaj narrated to us, he said: Layth narrated to us, he said: Sa’id al-Maqburi narrated to me, from his father, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) used to say: "O Muslim women, let no neighbor consider insignificant [a gift] for her neighbor, even if it be the trotter of a sheep."