Hebrews 10:19-20 in the King James Version of the Bible reads: "Having therefore, brethren, boldness to enter into the holiest by the blood of Jesus, by a new and living way, which he hath consecrated for us, through the veil, that is to say, his flesh."

This passage from the book of Hebrews speaks to the reconciling work of Jesus Christ and the access that believers now have to God through Him. The themes present in this verse include redemption, sacrifice, and access to God.

The context of this passage is important to understanding its significance. The book of Hebrews was written to a group of Jewish Christians who were in danger of reverting back to Judaism due to persecution and pressure from the Jewish community. The author of Hebrews sought to remind them of the superiority of Jesus and the new covenant that He established through His sacrifice.

The passage begins with the phrase "having therefore, brethren," indicating that what follows is a conclusion or result of a previous argument. The author is building upon the previous discussion of Jesus as the ultimate high priest and the one who has made atonement for the sins of humanity once and for all. As a result of this atonement, believers now have "boldness to enter into the holiest by the blood of Jesus." This boldness signifies the confidence and freedom that believers have in approaching God because of the atoning work of Christ.

The reference to "the holiest" alludes to the Most Holy Place in the tabernacle or temple, which was the innermost sanctuary where the presence of God dwelt. In the Old Testament, access to this sacred space was restricted to the high priest, and only once a year on the Day of Atonement. However, through the blood of Jesus, believers now have unfettered access to the presence of God.

The phrase "by a new and living way" emphasizes the contrast between the old covenant and the new covenant. The old way of approaching God through animal sacrifices and human mediators has been replaced by a new and living way, which is Jesus Christ Himself. This new way is "living" because Jesus conquered death through His resurrection, and it is "new" because it inaugurates a new era of relationship between God and humanity.

The passage then states that Jesus has "consecrated for us, through the veil, that is to say, his flesh." The reference to the "veil" alludes to the curtain that separated the Most Holy Place from the rest of the temple. When Jesus died on the cross, this veil was torn in two, symbolizing the removal of the barrier between God and humanity. This tearing of the veil represents the access that believers now have to the presence of God through the flesh of Jesus, which was sacrificed for the sins of the world.

Overall, Hebrews 10:19-20 conveys the central message of Christianity, which is the reconciling work of Jesus Christ. Believers are no longer separated from God by sin and the requirements of the old covenant. Instead, they have been given boldness and freedom to enter into the presence of God through the atoning sacrifice of Jesus. This passage serves as a powerful reminder of the grace and mercy of God, and the unparalleled access that believers have to Him through the new and living way of Christ.