Question: How can the dead rise from their graves if they're already in heaven?
Response: It is the bodies that are dead, not the souls and spirits. Paul declares that at death the believers are "absent from the body... present with the Lord" (2 Cor:5:8We are confident, I say, and willing rather to be absent from the body, and to be present with the Lord.
See All...). The dead bodies of those who "sleep in Jesus" [i.e., whose bodies "sleep" in the grave but whose souls and spirits are in heaven] will rise to be reunited in immortality with the souls and spirits that return with the Lord from heaven (1 Thes:4:14-16 [14] For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.
[15] For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
[16] For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
See All...).