John 3:13

Jesus explained why He could speak authoritatively about heavenly things. No teacher had ascended into heaven and returned to teach about heavenly things. Evidently Jesus was referring to being personally present in heaven since, obviously, many prophets had received visions of heaven (e.g., Isaiah 6; cf. 2 Corinthians 12:2-4; Revelation 1:10-20). However the Son of Man descended from heaven so He could teach about heavenly things. The NIV translation implies that Jesus had already ascended into heaven, but that is not what the Greek text says. The Greek words ei me, translated "but" or "except," contrast a human who might have ascended into heaven and the God-man who really did descend from heaven. Jesus here claimed to be the Son of Man (Daniel 7:13-14) who had come from heaven to reveal God to humankind (cf. John 1:51).

"Throughout this Gospel John insists on Jesus’ heavenly origin. This is one way in which he brings out his point that Jesus is the Christ. Here his heavenly origin marks Jesus off from the rest of humanity." [Note: Morris, p. 197.]