Carol,You asked 2 questions.
1) Why does Revelation 3:5 say He who overcomes shall be clothed in white garments; and I will not ERASE or BLOT or REMOVE his name from the book of Life?
I believe that eternal salvation cannot be lost. Everyone who accepts Christ will be saved and has a place waiting for them in heaven. But I also believe that the rapture is a special reward. In fact, those who long for Christ's return (watching, ready and waiting) they are promised a special crown!Revelation 3:11
Amplified Bible (AMP)
11 I am coming quickly; hold fast what you have, so that no one may rob you and deprive you of your crown.
Crown of Righteousness (a.k.a. the Watcher’s Crown) For loving (longing for) the Lord’s appearing (2 Timothy 4:8)
2 Timothy 4:8
New King James Version (NKJV)
8 Finally, there is laid up for me the crown of righteousness, which the Lord, the righteous Judge, will give to me on that Day, and not to me only but also to all who have loved His appearing.
This is a special crown and I think those who are ready at the time of the pretribulation rapture can expect this crown. All of the crowns are rewards!
Here is your second question: 2) In reference to the 10 virgins, can it be possible that the 5 foolish virgins were /are unconverted religious Jews?
Insofar as they are all listed as virgins and would have all been taken by the bridegroom if they were all ready at His appearing, I can only conclude that they represent the two groups I mentioned... ready Christians and those Christians who will have to endure at least part of the tribulation. Please note that matyrs are offered different crowns as their rewards.
I feel inadequate to explain this much better but I hope you can see from my response why I believe as I do.
YBIC
Bruce Baber