John 3:18:

He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.

See also:

Sickness as Chastening and Judgment in the New Testament
Can Sickness Be the Wrath of God Abiding on a Sinner (John 3:36)?
Objection: John 14:12 in the Greek is Collective – We Collectively Do Jesus’ Works but No One Person Will Do Them
Notes on 1 Corinthians 11:27-32