Musnad Ahmad 30:818

Yazid narrated to us, Hammam ibn Yahya informed us, from Qatadah, from an-Nadr ibn Anas, from Bashir ibn Nahik, from Abu Hurairah, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever has two wives and inclines toward one of them over the other, he will come on the Day of Resurrection dragging one of his sides, fallen or leaning." (Yazid was in doubt [as to which word was used]).