SCRIPTURE Hebrews 10:14 “For by one offering he hath perfected for ever them that are sanctified.”

This appears as a bit of a translation error in the KJV. Although the word perfected is perfect tense, the word sanctified is in the present tense. The second part of the passage qualifies the first part. The rendering of the KJV seems to suggest that sanctification (“sanctified”) is a past tense verb. It is not. We choose whether or not to follow the Holy Spirit which leads our sanctification as shown by the voice and tense in Romans 12:2. We have the free will to follow or resist the Holy Spirit. One leads to eternal life, the other to eternal misery (ex. Romans 8:13, others). These are the reason for the teachings not to resist, grieve or quench the Holy Spirit. So the first part of this passage holds true as long as we are being sanctified. We are not being sanctified if we turn away from Christ. We are not being sanctified if we turn back to the law. We are not being sanctified if we are living in sin. Again, the first promise is conditional on the second part of the verse in which we play a role. Thus, it is not an open-ended statement about eternal security without a conditional aspect.