'The first resurrection,' mentioned in Revelation 20:5, 6, does not mean a first resurrection, but the essence and primary part of resurrection, which is salvation and eternal life. There is only one resurrection to life. A second does not happen, and is not mentioned anywhere in the Bible.

(References: Apocalypse Explained 6; Apocalypse Revealed 851; Revelation 20:5-6)

The number "four" in the Bible represents things being linked together or joined. This is partly because four is two times two, and two represents the ultimate linking between our desire to be good and our understanding of truth. We can also see this in the fact that most buildings are rectangular, with the four sides linking together to make a whole. We also divide directions into four -- north, east, south and west -- and talk about the "four corners" of something meaning all of it. So our special thinking naturally looks at four sides as linking together into a whole.

(References: Apocalypse Explained 417; Arcana Coelestia 1686, 9103, 9601, 9767, 9864)