John 3:3 is the 'earthly thing' Jesus refers to in John 3:12 — the teaching on being born again that Nicodemus struggles to believe.

John 3:5 specifies another 'earthly thing' — being born of water and Spirit — which Jesus says Nicodemus fails to accept in John 3:12.

John 3:8 gives the wind analogy — an 'earthly thing' that Nicodemus doesn't grasp, which John 3:12 references as the basis for greater truths.

John 3:13-17 provides the heavenly truths Jesus refers to: the Son of Man descending, being lifted up, and offering eternal life.

John 3:31-36 expands on the contrast: the one from heaven speaks God's words and gives eternal life, reinforcing Jesus' point about heavenly things.

John 1:1-14 reveals the Word became flesh — the ultimate heavenly thing Jesus speaks of, grounding his authority to declare divine truths.

1 Timothy 3:16 encapsulates the mystery of godliness — Christ incarnate and exalted — which is the heavenly truth Jesus says cannot be believed.

1 Corinthians 15:47 distinguishes the earthly man from the heavenly man—underscoring Jesus' heavenly origin that enables him to speak of heavenly things.

In Romans 10:6, Paul argues faith does not require ascending to heaven because Christ has come down—reinforcing Jesus' point about heavenly revelation from above.

1 Corinthians 2:7-9 describes God's hidden wisdom revealed by the Spirit, similar to Jesus' point that heavenly truths require belief beyond earthly understanding.

1 Corinthians 3:1 contrasts worldly and spiritual, similar to John 3:12's contrast between earthly and heavenly — inability to receive deeper revelation.

1 Corinthians 3:2 speaks of milk not solid food — paralleling John 3:12's idea that unbelief in earthly things prevents understanding heavenly ones.

In Hebrews 5:11, the author laments dull hearing, mirroring Jesus' frustration that Nicodemus cannot believe earthly things, let alone heavenly.