All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is not incumbent on the spouses to sleep together in the same bed, but it is better for them to sleep in one bed, unless they need to sleep in separate beds for some reason. An-Nawawi underlined this meaning in his commentary on Saheeh Muslim and explained that it is a manifestation of the (enjoined) mutual kindness between the spouses and that it was the practice of the Prophet, sallallaahu ‘alayhi wa sallam, with his wives. There is no doubt that sharing the same bed fosters mutual affection and intimacy between the spouses, and leaving it may cause estrangement, and therefore, as much as possible, they should not sleep in separate beds. The Islamic Sharee‘ah enjoins both spouses to live with one another in kindness; Allah, The Exalted, Says (what means): {…And due to the wives is similar to what is expected of them, according to what is reasonable...} [Quran 2:228]
It is incumbent on a wife to obey her husband if he invites her to sleep with him in the same bed because she is commanded under the Sharee‘ah to obey him in what is good and permissible. It should be noted that the wife’s obedience to her husband is pertinent to marriage and its implications, and it is not absolute obedience. It was narrated on the authority of Abu Hurayrah that the Prophet, sallallaahu ‘alayhi wa sallam, said: “If I were to command anyone to prostrate before anyone (besides Allah, The Exalted), I would have commanded the wife to prostrate before her husband.” [At-Tirmithi]
We do not know of any evidence indicating that it is obligatory on a husband to obey his wife when she invites him to sleep with her in the same bed. But it is recommended for him to do so, as we mentioned above, because it is a manifestation of the enjoined mutual kindness. The religious rulings are determined based on the Sharee‘ah rather than people’s personal inclinations, and the Sharee‘ah does not favor one gender at the expense of the other. The very essence of faith entails submission to Allah, The Exalted, and compliance with His Rulings. There is no doubt that there is great knowledge and wisdom behind them and people may or may not perceive that wisdom. Allah, The Exalted, Says (what means): {But no, by your Lord, they will not [truly] believe until they make you [O Muhammad] judge concerning that over which they dispute among themselves and then find within themselves no discomfort from what you have judged and submit in [full, willing] submission.} [Quran 4:65]
Allah Knows best.