Qurtubi said his commentary on Sahih Muslim:

It has been rigorously authenticated from the Prophet (Allah bless him and give him peace)

(1) that "the earth does not consume the bodies of prophets"; and

(2) that the Prophet (Allah bless him and give him peace) met [previous] prophets on the night of his miraculous night-journey to Jerusalem both in al-Bayt al-Maqdis and in the heavens, particularly Musa (Allah bless him ad give him peace), who he saw standing praying in his grave; and

The Prophet (Allah bless him and give him peace) also told us that Allah Most High returns his spirit to him so that he can return the greeting (salam) of everyone who greets him. Many other hadiths that corroborate this fact have also been transmitted from him.

As for his (Allah bless him and give him peace) saying, "The earth consumes every child of Adam and returns him to his origin, namely, earth," this is a general statement [whose generality is not intended absolutely, but] particularized by the hadiths, (1) "Allah Most High has forbidden the earth from consuming the bodies of prophets," and (2) "A sincere muezzin is like someone who is lying covered in blood," whose outward purport indicates that that the earth does not consume the bodies of martyrs or sincere muezzins. This has also been witnessed with respect to martyrs who have been found a long time after being buried, as mentioned in books about the life of the Prophet (Allah bless him and give him peace) and other books. [end quote from Qurtubi's commentary on Sahih Muslim]

Abu Dawud relates that the Messenger of Allah (Allah bless him and give him peace) said, "Friday is one of the best of your days: on it was Adam created, on it did he die, on it will the Trump be blown, and on it will the final hour be. So bless me much on that day, for your blessings will be presented to me." The Companions said, "O Messenger of Allah: how will our blessings be presented to you when you have decayed?" He said, "Allah Mighty and Majestic has forbidden the earth from consuming the bodies of prophets."

In addition to all of the above, Allah Most High says, "Think not those who are slain in the path of Allah to be dead; they are alive and provided for with their Lord." (Quran, 3:169)

From all of the above, we can infer the following:

(1) The bodies of prophets do not decay in their graves, and they are alive in their graves. This life is different from the live that they had in this world, and also different from the life that they will have after resurrection, but it is a life nevertheless. In reality, everyone who dies has an interworldly life because death is not annihilation, but a transfer into another realm of existence. The interwordly life of the prophets, however, is more complete than anyone else.

(2) Martyrs, too, are alive in their graves, in accordance with the Quranic verse quoted above. This life is different than the life that they lived in this world, and different than the life that they will live after resurrection, but it is a life nevertheless, and one that is more complete than the interworldly lives of normal people. Reports in the sira mention that the Companions who died in the Battle of Uhud remained undecayed when they were uncovered a long time later. There are also several such narrations from the era of the Companions and afterwards. These historical reports do not, however, decisively indicate that their bodies will remain undecayed until the end of the time (like the bodies of prophets), nor do they decisively indicate that this is true of every martyr.

To summarize, there are clear hadiths that indicate that the earth does not consume the bodies of prophets, and that they are live in their graves, there is a clear verse that mentions that martyrs are alive in their graves, and there are several historical reports that mention that the bodies of martyrs were uncovered a long time after their burial and found undecayed.