The Holy Bible says,

That is why the Good News was preached to those who are now dead;

so although they were destined to die like all people,

To be absent from the body is to be present with the Lord (2 Corinthians 5:8).

in that "the spirit returns to God who gave it." (Ecclesiastes 12:7).

And I declared that the dead, who had already died,

are happier than the living who are still alive. (Ecclesiastes 4:2).

Blessed are the dead who die in the Lord....(Revelation 14:13).

Actually,

looking at Revelation gives us a better idea of where the dead in Christ are. We see the souls of those martyred under the alter in heaven. They have not yet received their new bodies yet so I suppose that all who die in Christ go under the alter in heaven. Until they receive their new bodies at the resurrection.

Those shown around the throne therefore in Revelation are the Old Testament saints. They received their new bodies when Jesus resurrected. This is why it states that many of the saints rose when Jesus rose from the dead. They received their new bodies. All Old Testaments saints that is.