God’s Word provides a larger picture of salvation than just “I am justified” or “Once saved always saved.” Indeed I am justified when I place my faith in Christ, but I am also united to Him, sanctified, being sanctified, and guaranteed a glorified, resurrected body. My salvation is not just a one time event. It is a past (“were reconciled” Rom 5:10), present (“being justified” Rom 3:24), and future event (“Shall be saved” Rom 5:10). The time and theological nuances of salvation come together in the doctrines of perseverance and preservation.
God promises to preserve those who turn to Him. You will have eternal life. Salvation is an inheritance, imperishable and undefiled, it will not fade away, and reserved in heaven for you (1 Peter 1:3-4). John 6 teaches God will preserve His children to the end, “All that [the Father] has given to [Christ] I lose nothing, but raise it up on the last day” (John 6:39).
God also says the believer needs to persevere to the end. One key theme in Hebrews is the doctrine of perseverance. Hebrews teaches the believer is responsible to endure to the end.
Hebrews 3:6 and 3:14 slam dunk teach the doctrine of perseverance. Both verses, grammatically, lexically, and contextually teach the believer is responsible to “hold fast” to the end. This does not mean the person is responsible for his or her salvation, but it does teach culpability and should encourage us to continually look to Christ as we live (Hebrews 12:1-3).
Both Hebrews 3 passages declare the end result of holding fast: You are in Christ’s house and you are partakers of Christ. This is the end goal. The end in sight is to be in God’s family, partaking of heaven, with Christ, having eternal life and being with God. How did you get these? “If you hold fast the beginning of our assurance firm until the end” and “if we hold fast our confidence and the boast of our hope firm until the end.”
God sets up both sentences with an “if . . . then” logic. If you do the first part, then you will receive the second part. If you hold fast until the end, then you receive the prize.
The word “hold fast” comes from κατέχω, meaning “to adhere firmly to traditions, convictions, or beliefs, hold to, hold fast.”  Luke 8:15 uses the word with a similar context and point of Hebrews 3, “But the seed in the good soil, these are the ones who have heard the word in an honest and good heart, and hold it fast, and bear fruit with perseverance.”
The believer adheres firmly to Christ, His work, and the truth of the Gospel until the end. In Hebrews 3, the author warns the reader to hold fast the faith until the end. Something the Israelites who left Egypt were unable to do. Their example warns us regarding the danger of falling away, encouraging us to believe until the end.
God preserves His children. And His children need to fix their eyes on Jesus, the author and perfecter of our faith. Both are true. “Consider Him, who endured such hostility by sinners against Himself, so that you will not grow weary and lose heart!” (Hebrews 12:3)
 Hebrews 2:1; 3:6, 12, 14; 4:2, 6, 11, 14-16; 6:1, 4-6, 11-12; and 12:1-3 to name a few.
 BDAG, 533.