The Prophet ﷺ said: When a man has two wives and he is inclined to one of them, he will come on the Day of resurrection with a side hanging down. (Using translation from Abū Dāʾūd 2133)  

عَنِ النَّبِيِّ ﷺ قَالَ «مَنْ كَانَتْ لَهُ امْرَأَتَانِ فَمَالَ إِلَى إِحْدَاهُمَا جَاءَ يَوْمَ الْقِيَامَةِ وَشِقُّهُ مَائِلٌ»