Jude 1:7 - Even as Sodom and Gomorrah, and the cities around them, having, in the same way as these, given themselves over to sexual immorality and gone after strange flesh, are shown as an example, suffering the punishment of eternal fire.
Matthew 25:46 - These will go away into eternal punishment, but the righteous into eternal life."
Hebrews 9:27 - Inasmuch as it is appointed for men to die once, and after this, judgment,
Matthew 10:28 - Don't be afraid of those who kill the body, but are not able to kill the soul. Rather, fear him who is able to destroy both soul and body in Gehenna.
2 Corinthians 6:14 - Don't be unequally yoked with unbelievers, for what fellowship have righteousness and iniquity? Or what fellowship has light with darkness?