What is the ruling on burying a woman with her husband, and the reverse?

Question:
Is it permissible for a woman to be buried with her husband, or the reverse, in a single grave?

Answer:
The Sunnah is to avoid that; the Sunnah is for each person to be alone, the man alone and the woman alone, and so it is with the rest of the people. This is how the Prophet (peace and blessings be upon him) did in al-Baqi' with the Companions; they buried each person alone.
However, if dire necessity and pressing need require such a thing—for example, if a plague descends and many people die, or if there is fighting and a great battle occurs, resulting in many dead such that it is difficult to separate each one—then it is permissible to combine men and women, and it is permissible to combine two or three men, as the Prophet (peace and blessings be upon him) did on the day of Uhud. On the day of Uhud, he buried two or three men in a single grave out of dire necessity and pressing need, because the number of casualties was great and the Muslims had wounds, so they needed this. There is no harm in a woman being buried with her husband; there is no harm in the case of need. But in the absence of need, when the number of dead is few... it is not permissible to combine two or three except for dire necessity and pressing need.