What does John 3:32 mean?
Jesus' message is based on His own first-hand knowledge. This is why He is the only valid source of spiritual truth. Only Jesus has come from Heaven (John 3:13). Only those who believe His message can be saved (John 3:18). Those who won't listen to the common, ordinary things Jesus teaches have no hope of understanding the spiritual things (John 3:12). The Greek word translated "testimony" is martureo, which means "to report," or "to affirm," in the same sense that a person's statement in court is called their "testimony." The apostle John uses this term very often, more than 30 times in this gospel, and 40 times overall (John 1:7; John 5:36; John 19:35; John 21:24).Jesus' claim to personal knowledge is one reason He often uses the phrase, "amen, amen." The word amen has been preserved from translations through Greek, Hebrew, and into English. This is usually translated as "verily, verily," or "I tell you the truth," or "I assure you." Starting a statement with this phrase is a way of claiming personal knowledge—not something learned and repeated, but an original, intimately-known fact.
Sadly, most people will not accept the message of Christ. The end of verse 32 uses a common technique of exaggeration. We do the same in modern speech: when one in one-hundred people accept something, we might say, "no one thinks that's true." In reality, someone does, but the point is clear. Here, in the context of the very next verse, we see what John means. Very few accept the Light (John 1:9–10), because it forces them to confront their sins (John 3:19).