As I already previously explained in Hebrews 3:14 - For we
have become [past tense Greek 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.
The verb is uses the perfect tense (Greek gegonamen). There is nothing here that implies we will become or will remain partakers of Christ if we hold fast to the end.
The perfect tense in Greek is used to describe a completed action which produced results which are still in effect all the way up to the present. Notice that the perfect tense carries two ideas: (1) completed action and (2) continuing results. The action was completed at some time in the past, and the results continue up to the present.
Wuest - "The
evidence of the fact that the recipient
is saved, is that he
retains his profession of faith in Messiah under the stress of persecution, not going back to the 1st Covenant sacrificial system and works orientation of the Pharisees. (Heb 3:12-14).
The question is not one of the retention of salvation based upon a persistence of faith, but of the possession of salvation as evidenced by a continuation of faith." The translation reads, therefore, “For we became partakers of Messiah with the present result that we are partakers of Him.” That is, if these first-century Jews would
maintain their faith in Messiah to the end of their lives, that would show that they had become in the past partakers of Messiah, and that as a present result they were partakers of Him. Again as in Hebrews 3:6,
the question is not one of the retention of salvation based upon a persistence of faith, but of the possession of salvation as evidenced by a continuation of faith. The perfect tense reaches back into the past and then speaks of the present. It is not the future of these Jews that the writer is concerned about here, but he is concerned as to whether in times past and as a result at the time of the writing of the epistle they were partakers of salvation in Messiah. (
Hebrews - Wuest's word studies from the Greek New Testament )