Note 13 at Jn. 5:28: Jesus had just spoken of the miracle of someone being resurrected from spiritual death to new life in Jesus (vv. 24-25). He is now saying if we're amazed at that, we will certainly be amazed when we see all the physically dead bodies resurrected at the end of the world.

Note 14 at Jn. 5:28: No one is actually in the grave. The Bible does not teach a "soul sleep" as some people try to make it say. At physical death, the soul and the spirit separate from the body (Jas. 2:26 with Rev. 6:9) and either go immediately to be with the Lord (Lk. 23:43; 2 Cor. 4:6-8; 5:1-10; Phil 1:23) or to hell (also Hades or Gehenna--see note 13 at Mt. 5:22, p. 75; Lk. 16:22-23). Our physical bodies remain in the graves and return to dust (Gen. 3:19).

The word "grave" distinguishes that Jesus is speaking about our physical bodies. Our physical bodies will be resurrected and reunited with our spirit and soul to spend eternity in either the New Jerusalem with Christ (see note 21 at Jn. 5:43, below; Rev. 21:10-27) or the lake of fire with the devil and his angels (Rev. 20:14-15; 21:8).