From the NASB..Hebrews 6:1-3 and 4-6
1.Therefore leaving the [
a]elementary teaching about the [
b]Christ, let us press on to [
c]maturity, not laying again a foundation of repentance from dead works and of faith toward God, 2 ofinstruction about washings and laying on of hands, and the resurrection of the dead and eternal judgment. 3 And this we will do, if God permits.
Hebrews 6:1-3 is pretty clear, You have laid the foundation, you know your ABC's now move forward and let God carry you along to maturity.
4 For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit, 5 and have tasted the good word of God and the powers of the age to come,6 and
then have fallen away, it isimpossible to renew them again to repentance, [
d]since they again crucify to themselves the Son of God and put Him to open shame.
"For In the case of those" seems like the writer is describing a hypothetical case to prove his point that a true believer cannot lose his salvation. 6:9 seems to support that. ...."9. But, beloved, we are convinced of better things concerning you, and things that[
h]accompany salvation, though we are speaking in this way."
Look at 4 compared to 1-3, the writer changed the pronouns from "we" and "us" to "those".