The word “if” means condition.
"if" indeed we continue in the faith firmly established and steadfast, and not moved away from the hope of the gospel,
we confirm that He has now reconciled us in His fleshly body through death, in order to present us before Him holy and blameless and beyond reproach.
Just as in 1 Corinthians 15:1-2, we read - Moreover, brethren, I declare to you the gospel which I preached to you, which also you received and in which you stand, by which also you are saved,
IF you hold fast that word which I preached to you--
unless you believed in vain. To
believe in vain is to
believe without cause or without effect, to no purpose. Those who fail to hold fast to the word (the gospel) that Paul preached in 1 Corinthians 15:1-4, demonstrated that they
"believed in vain" (did not truly believe the gospel). Their belief was
never firmly rooted and established from the start. Hence,
IN VAIN.
Hebrews 3:14 - For we
have become [past tense Gk. verb, gegonamen, meaning we have become already] partakers of Christ, (demonstrative evidence)
IF we hold fast the beginning of our confidence steadfast to the end. Notice that this is essentially a repeat of verse 6, in which we read: but Christ was faithful as a Son over His house -
whose house we are, (demonstrative evidence)
IF we hold fast our confidence and the boast of our hope firm until the end.
The wording is not - "and you will become partakers of Christ (future indicative) if you (future indicative) hold fast." It is rather - "you
have been, and now are partakers of Christ" (demonstrative evidence)
IF in the future you hold fast the beginning of your confidence steadfast to the end."
Holding fast confirms "have become" partakers of Christ.
The point is that not all of these Hebrews have become partakers in Christ and the only ones in the end who will be identified as having become partakers of Christ (demonstrative evidence) will be those who have held fast the beginning of their confidence steadfast to the end. Now what about those faltering Hebrews who depart from God, yet begin with loud confidence and profession of loyalty? But then later? Once again,
holding fast confirms "have become" partakers of Christ.
In Hebrews 4:1-2, we read - "For indeed
the gospel was preached to US as well as to THEM; but the word which THEY heard did not profit THEM, not being mixed with faith in those who heard it. For
WE who have believed do enter that rest, as He has said: "So I swore in My wrath, 'They shall not enter My rest," although the works were finished from the foundation of the world. Obviously, not all of these Hebrews were genuine believers. *Notice that verses 2-3 make a
distinction between US who have BELIEVED and do enter that rest and THEM who heard the word but did not mix faith with what they heard and will not enter that rest because of UNBELIEF.
Jude 1:5 - ..the Lord at one time delivered his people out of Egypt, but later
destroyed those who did not believe.