What does Luke 9:24 mean?
Luke's book presents what some call the "reverse gospel." He shows that everything we think we know about success and preserving our life in this world ultimately leads to failure and eternal death. The disciples want to be great in Jesus' coming kingdom; they don't know the kingdom is thousands of years away and that the least will be the greatest (Luke 9:46–48). They think they need to carefully protect the inner circle, not understanding Jesus' circle is far wider than they could imagine (Luke 9:49–50; Acts 10:34–35). They think they need to assert their authority on behalf of Jesus' honor (Luke 9:51–55); they don't understand that if a non-believer rejects Jesus, all the believer need do is leave, not fight (Luke 9:5).If the disciples had joined the crowd in rejecting Jesus, they would not have received His life. If they had defended their worldly position in Christ, they wouldn't have been able to build the church and spread Jesus' good news of salvation. They would have lost everything at the crucifixion, as Judas did, and not received the life of the Holy Spirit at Pentecost (Acts 2). Only by laying down their earthly ambitions could they find their place in God's kingdom.
This verse is not saying those who die for claiming loyalty to Jesus will automatically be saved. Martyrdom does not earn someone a ticket to heaven. Salvation is based on God's grace received through faith (Ephesians 2:1–10). It has to do with our relationship with Jesus, not the manner of our death. It is the one who is unashamed of Jesus, His words, and His cross—who believes His words about salvation and follows Him—who will be saved (Luke 9:26).
"Life" has a broad meaning in Greek. Psychē can refer to the potency that animates a body (breath or spirit), the "inner person" in general (soul or heart), or the soul as the part of a person that is not extinguished at death. Jesus is using a play on words: if we deny Him to save our physical life on earth, we will lose the eternal life He promises us. When Christ-followers die and receive their resurrected bodies, we will not be animated by our fragile organs; the Spirit (Romans 8:11) will provide that life.