Here's a repost of my recent reply to the thread entitled, " Our future sins are not already forgiven? Your thoughts?" :
In my opinion, the foremost single passage in scripture presenting overwhelming evidence that all of a believers future sins have been covered at the moment of their regeneration is found in Hebrews 10:14. Again, it's necessary to make it clear that what I'm specifically addressing here is future sin as it relates to a believer's justified standing before God.
Hebrews 10:14, "For by one offering he hath perfected for ever them that are sanctified." [KJV].
Hebrews 10 :14 - Greek interlinear :
"By one [mia] for [gar] offering [prosphora] He has perfected [teteleiōken] for all time [eis to diēnekes] those [tous] being sanctified [hagiazomenous]."
"He has perfected" - root - Strong's #5048. teleioó
teleioó: to bring to an end, to complete, perfect
Original Word: τελειόω
Part of Speech: Verb
Transliteration: teleioó
Phonetic Spelling: (tel-i-o'-o)
Definition: to bring to an end, to complete, perfect
Usage: (a) as a course, a race, or the like: I complete, finish (b) as of time or prediction: I accomplish, (c) I make perfect; pass: I am perfected.
"being sanctified" - root - Strong's #37. hagiazó
hagiazó: to make holy, consecrate, sanctify
Original Word: ἁγιάζω
Part of Speech: Verb
Transliteration: hagiazó
Phonetic Spelling: (hag-ee-ad'-zo)
Definition: to make holy, consecrate, sanctify
Usage: I make holy, treat as holy, set apart as holy, sanctify, hallow, purify.
Generally speaking, those of the LOS [Loss Of Salvation or "Loss of Justification"] camp emphasize the aspect of the singularity of Christ's sacrifice [i.e. - it's completeness and sufficiency for the forgiveness and redemption of humanity throughout all of history] ... "For by one offering." That is, Christ had offered for all time a single sacrifice for sins [forever abolishing the need of it's repetition, as well as the Old Covenant sacrificial system]. It was Christ's singular act of atonement that provided a perfect and acceptable sacrifice which alone could satisfy God's holy righteousness and justice].
On the other hand, the opposing camp, the OJAS ["Once Justified, Always Justified"] or OASAAS ["Once Actually Saved, Always Actually Saved"] advocates by and large focus upon the resulting effect of Christ's singular sacrifice upon those who have placed their faith in it's efficacy and sufficiency to obtain their right-standing before God ... "he hath perfected for ever [for all time] them that are sanctified [those being sanctified]." To state it in a slightly different manner for further clarity ... "those being sanctified" - all those who, from age to age, through faith receive as their own that which has been procured for all men.
Although it is true that we do not have an "either/or", but rather a "both/and" scenario in view here [each camp representing one-half of the dual truths declared in Hebrews 10:14], it appears to me that there is compelling evidence contained within Hebrews 10:14 which supports the OJAJ position.
A critical question that needs to be addressed here is the following :"Should we view the sanctification spoken of here ["those being sanctified"] in a positional or progressive sense?"
Although it certainly appears to me that positional sanctification is in view here, a person's perspective on this issue actually matters little as it pertains to the question of the forgiveness of a regenerated person's future sin [as I will attempt to demonstrate by the following truth claims].
(1) A person cannot be progressively sanctified unless he/she has already been positionally sanctified [or set apart by God and considered to be holy in His eyes].
post #124 - page 7 <
https://www.christianforums.com/threads/can-a-genuine-blood-bought-regenerated-believer-forfeit-their-salvation.8214696/page-7 >
(2) A person cannot be sanctified in either a positional or progressive sense without also experiencing a justified status before God. [1 Corinthians 6:11].
(3) All those who have been justified will also be glorified [in both it's "already" and "not yet" dimensions]. Although glorification is viewed as including a present [continous] sanctifying/transformational work of the Holy Spirit operating in the lives of believers, there is also a future aspect attached to it ... the reception of a glorified body - a resurrection body in Heaven.
post #92 - page 5 <
https://www.christianforums.com/threads/can-a-genuine-blood-bought-regenerated-believer-forfeit-their-salvation.8214696/page-5 >
post #103 - page 6 <
https://www.christianforums.com/threads/can-a-genuine-blood-bought-regenerated-believer-forfeit-their-salvation.8214696/page-6 >
Therefore, positional and progressive sanctification, as well as the [ultimate] redemption of the body, are states that will be actualized in all of those ["from age to age"] who experience a justified status before God by way of the new birth ... "For if we have been united with him in a death like his, we shall certainly be united with him in a resurrection like his." - Romans 6:5 [English Standard Version].