Revelation 20:6

20:6 Blessed and holy is the one who takes part in the first resurrection. The second death has no power over them, but they will be priests of God and of Christ, and they will reign with him for a thousand years.

Revelation 20:14

20:14 Then Death and Hades were thrown into the lake of fire. This is the second death – the lake of fire.

Revelation 21:8

21:8 But to the cowards, unbelievers, detestable persons, murderers, the sexually immoral, and those who practice magic spells, idol worshipers, and all those who lie, their place will be in the lake that burns with fire and sulfur. That is the second death.”