Musar על עירובין 105:4

Our sages in Eruvin 53a have said that the reason the cave Abraham and Sarah were buried in is called מערת המכפלה, is from the word כפול, twin, or double, an appropriate name for a grave containing husbands and their wives, i.e. זוגות. What advantage is there in the fact that this cave houses the remains of husband and wife respectively? The meaning of our sages is that these pairs are all united with one another, that they are not separate pairs. Once the last of the four pairs, i.e. Jacob came to burial whose מטתו שלמה, whose "bed" was complete (since Leah had born him six sons and one daughter whose name was דינה),this symbolized the six days of creation and the Sabbath.