1 John 5:16 provides the teaching on praying for sin not to death — gives context for the distinction in verse 17.

1 John 3:4 defines sin as lawlessness — adds the idea that sin is transgression of God's law.

James 1:15 vividly describes sin's progression from desire to death — a clear parallel to the idea of sin leading to death.

Romans 5:21 contrasts sin's reign in death with grace's reign to eternal life — directly relevant to the deadly sin concept here.