What does John 10:1 mean?

Jesus' words here continue without pause from the end of His conversation with the Pharisees who disputed His healing of the man born blind in chapter 9. Here, again, Jesus uses the "Amen, amen" construction. This uses a word which has come from Aramaic almost unchanged into many other languages. It expresses agreement or hopefulness when used at the end of a statement. When used at the beginning of a sentence, it implies that the speaker is presenting first-hand, absolute truth.

This is the first of three related-but-separate analogies Jesus will make using the concept of shepherding.

Jesus begins the first metaphor by stating that someone who climbs the wall of a sheep enclosure "is a thief and a robber." In that era, multiple flocks of sheep would be housed in a single walled-in enclosure. The sides were high enough to prevent sheep from getting out, and wild animals from getting in. This structure would have a single opening—and this was the only intended place for the sheep to come in or out. Anyone attempting to get into the pen without using the single door was, by definition, up to no good.

In the next verses, Jesus will continue to explain that only the legitimate shepherd can come in and out, and only that shepherd is approved by the gatekeeper. This teaching also relies on the unique way sheep naturally learn to respond only to the voice of "their" shepherd, and not to others.