What does John 8:51 mean?

This verse once again uses an Aramaic word which has survived into Hebrew, Greek, and even English: amēn. Used at the end of a statement, this word is a declaration of truth or of a hope that what has just been said will be fulfilled. It suggests that the speaker agrees with the former words. However, used at the beginning of a statement, it implies that what follows is absolute, original, first-hand truth. When Jesus says "Amēn, amēn," translated as "truly, truly," He is introducing a crucial fact.

Jesus has already pointed out that the men attacking Him have no interest in the message of God. He has used various expressions to convey this: they "do not believe" (John 8:46), they "do not hear" (John 8:47), "the word finds no place" in them (John 8:37), they "cannot bear to hear" the word (John 8:43). This rejection proves that these people "walk in darkness" (John 8:12). They have rejected the one and only source of spiritual truth (John 8:12), and so they will die in their sins (John 8:21) instead of finding forgiveness (John 3:36).

Jesus's words here are in contrast to those who do not "hear," "walk," or "believe" according to His message. Those who "keep His word," in this context, are those who express saving faith in God's Son (John 3:16–18). Those who reject Christ, however, are condemned to spiritual death (John 3:18; John 3:36).

Once again, as shown in the next verse, Jesus' opponents will misunderstand His message.