On Heb 10:26 (cf. vv. 26-31) and the question of whether an apostate can ever be restored, Catholic apologist Karlo Broussard wrote that:
The first thing we can say in
response is that the RSV translation “if we sin deliberately” does not reflect
the fact that the Greek word rendered “sin” is a present participle, which in
Greek conveys the idea of ongoing action. Thus, other translations render this
statement “If we go on sinning deliberately” (ESV), “if we deliberately keep on
sinning” (NIV, NET), “if we go on sinning willfully” (NASB), “if we willfully
persist in sin” (NRSV). The passage thus envisions not a single sin or fall
into sin, but an ongoing pattern of willfull sin that has not been repented of.
For our second response, we can
affirm the author’s statement, “There no longer remains a sacrifice for sins.”
But this doesn’t mean a person can never repent and be restored. IT means
that as long as the person remains an apostate, he can’t have the merits
of Christ’s death on the cross applied to him. In other words, if we refuse
what God has provided for our salvation, then we’re left with no means of
salvation at all. As W. Leonard puts it, such a person has “incapacitated
himself for the reception of ministrations by the paralyzing ingratitude of his
rejection of Christian riches and by his complete break from all contact with
the source of salvation” (W. Leonard, “The Epistle to the Hebrews,” in A
Catholic Commentary on Holy Scripture, eds. B. Orchard and E. F. Sutcliffe
[New York: Thomas Nelson, 1953], 1.164. Leonard here is referring to those
spoken of in Hebrews 6:4-6, but his line of reasoning applies here as well).
(Karlo Broussard, Meeting the Protestant Response: How to Answer Common
Comebacks to Catholic Arguments [El Cajon, Calif.: Catholic Answers Press,
2022], 270-71)