Musnad Ahmad 1156:35

Yahya ibn Sa'id narrated to us, he said: Thabit ibn 'Umarah narrated to us, he said: Raytah narrated to me, from Kabshah bint Abi Maryam, she said: I asked Umm Salamah, I said: Inform me of what the Messenger of Allah, peace and blessings of Allah be upon him, forbade his family from? She said: "He forbade us from crushing date pits for cooking, and from mixing raisins and dates."