And we desire that each one of you show the same diligence to the full assurance of hope until the end, that you do not become sluggish, but imitate those who through faith and patience inherit the promises. (Hebrews 06:11-12, NKJV).
There's a reason small, slimy invertebrates are called slugs - they're slow and leave a thick, sticky trail behind them. They literally always have their foot in their mouths and it takes them forever to make forward progress. To be sluggish, then, is to be like one of them.
Spiritual sluggishness is less obvious but equally sticky and bereft of progress, and there is only one effective remedy: diligent imitation of those who are not sluggish, who through faith and patience inherit the promises.
Note those two ingredients, faith and patience. Faith, the substance of things hoped for and the evidence of things not seen, and patience, an attitude of quiet, persevering dependence on the Lord. The writer of Hebrews desires his readers to be as un-forgetful as God, to not only minister to the saints, but join in following them in their pattern of fervency and hope-filled endurance until the end.
The result is receiving the full inheritance of eternal life promised by God through the death of His Son.
How does this square with eternal security? Do we have to endure to the end in order to somehow attain salvation? What about saving faith being the gift of God and not of works, lest anyone should boast? Does this mean that those who don't endure lose their salvation?
Consider how the Apostle John answers these issues with a single comprehensive example:
They went out from us, but they were not of us; for if they had been of us, they would have continued with us; but they went out that they might be made manifest, that none of them were of us. (1 John 2:19, NKJV).
Do you see the elegant equation and how it applies here in Hebrews, as well?
Endurance to the end is not a prerequisite, it is proof of salvation. If someone does not endure, if their sluggishness overtakes them, the conclusion that must be reached is that they were never true heirs of Christ. For if they had been, they would have endured, for He is able to make them stand.
Then why the repeated warnings about drifting, dullness, departing, and sluggishness? Because it is God graciously reminding us to examine ourselves to see that we are truly in the faith, to work out our own salvation with fear and trembling, for it is He who works in us both to will and to do for His good pleasure. Again, why? So that we become His and thus are assured of receiving the promises.
The warnings are for those who may think they are saved, for whatever reasons - family tradition, good works, ritualistic practice, outward righteousness without inward transformation - but who have not yet crossed the boundary from death to life; who have not yet put their full faith in Christ's substitutionary sacrifice of their behalf. It is a loving exhortation to come the full way into the Kingdom, and put aside all other hope.
Only those who will come to complete faith will hear the warnings and respond. All others will fall away back into the worldliness that they may have been emerging from, but who are too double-minded to commit.
Surely the saddest outcome imaginable is for a person, perhaps even a "good" person, to pass from this life under a false profession of faith. That is why throughout the New Testament God has placed benchmarks, roadsigns, danger signs, and health checks to prevent that most tragic destiny.
But we need to read and hear and obey in order to take full advantage of these exhortations.
We need to be in fellowship with other believers, and to observe and imitate those whose lives, words, and deeds are uncompromising proof of their membership in the family of God.
By doing so, we will not fall by the wayside, unless of course, we were never really His to begin with, nor will ever be.
For those persons who willfully remain ignorant, or willfully reject Christ, it would be better that they were never born.