Your version of the bible has led you astray.Hebrews 10:14
14because by a single offering He has made perfect for all time those who are being sanctified.
KJV..."For by one offering he hath perfected for ever them that are sanctified." (Heb 10:14)
Man is sanctified by the application of the Lord Jesus Christ's blood at their "immersion" into Him and into His death.'Being sanctified' is in the Greek Present tense. Here's an explanation of the Greek Present tense:
In English, we know that the present tense describes something happening right now. It informs us of the time when an action takes place.
In Greek, however, the present tense primarily tells us the type of action. The Greek present tense indicates continued action, something that happens continually or repeatedly, or something that is in the process of happening. If you say, for instance, “The sun is rising,” you are talking about a process happening over a period of time, not an instantaneous event. The Greeks use the present tense to express this kind of continued action.
In contrast, Greek uses the aorist tense to show simple action. An aorist verb simply tells you that something happened, with no indication of how long it took. Aorist is like a snapshot; present is like a video.
See, you have a problem. In this one verse the author tells us that we have been made perfect one time and that perfecting does not need to be repeated. We know that because the verb 'made perfect' is in the Greek Perfect tense. At first this seems to defend your 'sinless perfection' doctrine. But he can't be talking about sinless perfection, but rather a legal declaration of perfection, because in the same breath that he says we are perfect he speaks of the presently ongoing action of being sanctified - the process of living the set apart life we have been set apart to live.Greek Tenses Explained – Ezra Project
ezraproject.com
Perfect in the eyes of God, legally speaking, but progressing into actually being perfect. This is the revelation that set Luther free from the works justification theology of the Catholic church and started the Protestant Reformation. He says he was born again in that moment of revelation.
"By the which will we are sanctified through the offering of the body of Jesus Christ once for all." (Heb 10:10)
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