Sahih al-Bukhari 1351
Funerals (Al-Janaa'iz)
Can the dead body be taken out of its grave
Narrated Jabir: When the time of the Battle of Uhud approached, my father called me at night and said, "I think that I will be the first amongst the companions of the Prophet (ﷺ) to be martyred. I do not leave anyone after me dearer to me than you, except Allah's Messenger (ﷺ) 's soul and I owe some debt and you should repay it and treat your sisters favorably (nicely and politely)." So in the morning he was the first to be martyred and was buried along with another (martyr). I did not like to leave him with the other (martyr) so I took him out of the grave after six months of his burial and he was in the same condition as he was on the day of burial, except a slight change near his ear.