Jesus proclaimed to humanity that ultimate death is just for sinners (the sinless won’t stay dead).
• Gospels: “Jesus said, ‘by me, be sin free unto eternal life’”.
• Paul: “Through Jesus, become sin-free unto life”.
• John the Baptist: “Through Jesus, get cleansing-life”.
Biblically, God communicated to humanity that ultimate death is just for sinners (the sinless won’t stay dead).
• OT prophets: “God will raise up the righteous.”
• Jesus: “Sinless get eternal life; the rest stay dead.”.1
• Bible: “God WOULD keep sinless (& destroy sin).”.
Believers in Jesus would anticipate that their eschatologically resurrected bodies will resemble whatever Jesus's resurrected body was like.
• E.g. Paul takes it for granted that Christians all knew this.1
While many of Jesus's miracles suggested that God was on Jesus's side, the physical resurrection of Jesus directly by God (without mediation) is a particularly flashy firework as far as miracles go. This is relevant because the resurrection therefore would be a particularly persuasive way to establish once and for all to Jesus's apostles (etc.) that Jesus was truly from God.
• God (Biblically) raised other people from the dead.1