Musnad Ahmad 30:2960

Waki’ and Bahz narrated to us, they said: Hammam narrated to us, from Qatadah, from an-Nadr ibn Anas—Bahz said in his narration: He said: Qatadah narrated to us, from Bashir ibn Nahik, from Abu Hurairah, he said: The Messenger of Allah, peace and blessings of Allah be upon him, said: "Whoever has two wives and inclines toward one of them over the other, he will come on the Day of Resurrection with one of his sides drooping."