The fragrance of musk comes from grave of companions ( رضی اللہ عنہ): Muhammad Bin Sharjeel  رحمتہ اللہ علیہnarrates that when a fist full was taken from grave of Hazart Saad Bin Maaz ( رضی اللہ عنہ) then it was blooming with fragrance just like musk. Then Prophet ﷺ said Subhan Allah Subhan Allah which tells us the fact that this fragrance also reached the blessed face of Prophet ﷺ.  There is also one another incident that some person took a fist full of dirt from the grave of Hazrat Saad ( رضی اللہ عنہ) and when he looked at it was musk.

Hazrat Abu Saeed Khadri ( رضی اللہ عنہ) narrates that I was one of the people who dug up the grave for Hazarat Saad in Jannat ul Baquih . Whenever we used to dig up the grave and any part of dirt of grave when fell up on us then the fragrance of Musk came from us till the point we dug up whole grave.

Hazrat Jabir ( رضی اللہ عنہ) we announced that we will transfer the bodies of martyrs of Ghazwa Ahad . When Hazrat Maavia ( رضی اللہ عنہ) got this spring water started. When we dug up the body of his then his body was so soft that his hands and feet could be bent.   One more narration is that when these martyrs were taken out from the graves after forty years then still their bodies were fresh and their hands and feet were soft.  (Hyat us Sahaba)