“So I want to remind you, though you already know these things, that Jesus first rescued the nation of Israel from Egypt, but later he destroyed those who did not remain faithful.” Jude 1:5 NLT

Jude warned the Christians of his day that they had to contend for the faith because evil men had secretly slipped into their congregations. Jude wasn’t the only biblical writer to warn the fledgling church. For instance these words of Paul the apostle were recorded by the writer Luke.
“For I know this, that after my departing shall grievous wolves enter in among you, not sparing the flock.Also of your own selves shall men arise, speaking perverse things, to draw away disciples after them. Therefore watch, and remember, that by the space of three years I ceased not to warn every one night and day with tears.” Acts 20:29-31
The biblical warning is as relevant to us today as it was to the first century Christians. Now, Jude helps us to identify the “secret slipper-inners” by using three examples, the first of which is found in our Scripture for today, Jude 1:5.
As an aside I think it interesting the NLT asserts that it was Jesus who rescued the nation of Israel out of Egypt. You will notice that the other translations say it was “The Lord”. The actual word used in the work is “kyrios”-
he to whom a person or thing belongs, about which he has power of deciding; master, lord
a) the possessor and disposer of a thing
1) the owner; one who has control of the person, the master
2) in the state: the sovereign, prince, chief, the Roman emperor
b) is a title of honour expressive of respect and reverence, with which servants greet their master
c) this title is given to: God, the Messiah BLB Lexicon
Just thought it worth mentioning… now let’s move on!
Jude references the fact that though all the Israelites were liberated out of Egypt they were later kept from the promised land by unbelief…lack of faith (or faithfulness more on that in Jude Pt. 9). The “secret-slipper-inners” are first of all men (or women) who operate from the principle of sight rather than from the principle of faith. In short they are “believers” who have never believed the Word of God!
We used to sing a song “If Jesus said it I believe it it’s His word He cannot lie. If its written in the Bible I’ll believe it till I die. Though the mountains be removed and be cast into the sea if Jesus said it I believe it and that’s good enough for me.”
While I was singing this in youth group years ago another group of “church men” were dissecting the Bible trying to decide if Jesus actually said anything that was recorded in the Gospels and if Isaiah and Daniel were actually prophecies or just rabbinical forgeries.
You will first of all know a “slipper-inner” by their refusal to believe the Bible as fact.
More on faithfulness in Pt. 9