Just one important verse you may want to consider: John: 3:16 No where does God's Word tell us that we have to do anything to "keep salvation." There is nothing on this earth we can do
Star, the verse you quote renders the Greek verb believe in the continuous present tense. This means that the more accurate rendering of the passage is: That whosoever is continuously believing in Him should not perish (aor., once for all), but be having everlasting life. We stand or fail on our faith but in scripture we see dead faith, lost faith, shipwrecked faith, compromised faith, and faith moved to something else (our works for example). The Holy Spirit is there to help us thank God. God Bless
