What does John 3:34 mean?

Nearly 40 times in this gospel alone, John claims that Jesus has been sent from God. This is the reason the book was written (John 20:30–31), and Jesus' miracles are the primary evidence (John 5:36). Nicodemus recognizes Jesus' miraculous abilities as proof that He is sent by God (John 3:2). Jesus offers other reasons to believe, including the testimony of John the Baptist, and the information found in the Hebrew Scriptures (John 5:36–39). Since Jesus is the only valid source of knowledge about God (John 3:12–13), rejecting Christ means rejecting God (1 John 5:10).

In the Old Testament, certain people were given the Spirit of God for a limited time. These include certain prophets (2 Chronicles 24:20; Micah 3:8; 2 Samuel 23:2), various people (Numbers 24:2, 1 Samuel 19:20), and some of the Judges (Judges 3:10; Judges 6:34), including Samson (Judges 13—16). Jesus, however, has the Spirit of God continuously. This is why He is said to have the Spirit "without measure," or "without limit."

This permanent presence of the Spirit, and the fact that Jesus came from heaven, are important proofs that He is, in fact, God incarnate (John 1:1; John 1:14).