Hebrews 10 (NKJV):
38 Now the just shall live by faith;
But if anyone draws back, My soul has no pleasure in him.”
39 But we are not of those who draw back to perdition,
but of those who believe to the saving of the soul.
I suppose you see that this is talking about
believers who are classified as being "just".
Some of them "live by faith" (and all of what this entails),
and it would be nice to understand what the NT word "believe" really means
!
Some of them do not, but choose to "fall back" from the faith.
These unfaithful ones go to you know where.
BTW, Ephesians was written to "the faithful" believers (1:1), and so was Colossians (1:2).
Paul was NOT writing to the unfaithful believers in those churches.