Greek prōtotokos ek tōn nekrōn (Colossians 1:18, Revelation 1:5). Prōtotokos carries two overlapping senses in Hebraic usage: temporal priority (the first one born) and status priority (the heir, the preeminent one — Israel is called God's "firstborn" in Exodus 4:22 though she came late chronologically). "Firstborn from the dead" is therefore not a mere chronological note (others had been resuscitated before Christ — Lazarus, Jairus's daughter) but a status claim: Christ is the first permanently risen, the first glorified, the head and pattern of the new humanity.
The resurrection of Jesus is not a data point — it is the inauguration of the new creation. Lazarus rose to die again; Christ rose to die no more. "We know that Christ, being raised from the dead, will never die again; death no longer has dominion over Him" (Romans 6:9). As firstborn from the dead, He guarantees the resurrection of all who are united to Him: "in Christ shall all be made alive. But each in His own order: Christ the firstfruits, then at His coming those who belong to Christ" (1 Corinthians 15:22-23). The same power that raised Jesus physically and permanently works in believers now (Ephesians 1:19-20) and will raise them bodily at the last day (Romans 8:11). Colossians 1:18 also ties the title to Christ's headship of the Church — He is firstborn in both creation (v. 15) and new creation (v. 18), preeminent in every domain. The bodily resurrection of Christ is the most verifiable miracle in history and the load-bearing wall of the whole Christian faith (1 Cor 15:17).