Is expiation obligatory for one who swore that his wife would not sleep in his room, but she did sleep there? And what is it?

If you swore an oath that your wife would not sleep in your room, and then you allowed her to do so, you have broken your oath, and an expiation for breaking an oath is incumbent upon you. You have done well by allowing her to sleep in your room, as this resolves the problem and fosters harmony, for the Prophet, peace and blessings be upon him, said: "Whoever swears an oath and then sees something else as better than it, let him expiate for his oath and do it."