Whoever has two or more wives has to treat them fairly. It is not permissible for him to single out one of his wives with regard to spending, accommodation or spending the night, to the exclusion of the others. There is a stern warning issued to the one who has two wives and does not treat them fairly. It was narrated that Abu Hurayrah (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever has two wives and inclines more towards one of them than the other, will come on the Day of Resurrection with half of his body falling.”  According to another version: “Dragging half of his body which will be falling or leaning.” Narrated by Imam Ahmad in al-Musnad, 2/295, 347, 471. A similar hadeeth was also narrated by al-Nasaa’i and Ibn Maajah in their Sunans. 

And it was narrated from Abu Hurayrah (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “Whoever has two wives and inclines more towards one of them, will come on the Day of Resurrection with half of his body leaning.” Narrated by Abu Dawood in his Sunan, 2/601. Al-Tirmidhi narrated something similar in al-Jaami’. 

This evidence indicates that it is obligatory to treat co-wives fairly and equally, and that it is haraam for the husband to incline more to one of them in a way that will hurt the other. This does not include the inclination of the heart, for a person has no control over the inclination of the heart. Hence the Messenger of Allaah (peace and blessings of Allaah be upon him) used to divide his time equally among his wives, and he said: “O Allaah, this is my division of that which I can control, so do not take me to task for that over which You have control and I have no control” [meaning love in the heart]. 

Based on this, it is not permissible for this husband to single out one of his wives with regard to something over which he has control. If he gives a house etc to one of his wives, he must treat all his wives equally in that regard, and give a similar gift or something of equal value to all of them, unless the second wife allows that.