What does John 10:31 mean?

Ancient writers were far more concerned with themes, facts, and events than with perfect chronology. In other words, not everything written in texts like the gospel of John is assumed to happen in exactly that order. In this case, Jesus has been cornered in the temple complex (John 10:22). Solomon's colonnade included a sheer drop to the east, as well as a solid wall. The only escape route would have been back through the temple. The mob "gathered around," described using a Greek term meaning "surrounding and pressing in," and they issued a challenge to repeat controversial statements (John 10:24). This group of religious leaders is clearly hostile.

Though this verse says they "picked up stones," the implication is not that they reached down, at that precise moment, to find rocks. This encounter is well inside the temple grounds, and nowhere near easy access to the surrounding terrain. Stones suitable for an attack like this were not simply laying around the temple within reach. In other words, these men brought the rocks with them when they first surrounded Jesus. The Greek grammar involved here is not specific about "when" the act happened, only that it happened. In short, John is saying these men "had picked up" stones, anticipating violence. Jesus has given them all they need to justify following through on their threats (John 10:30).

As has happened in the past, however, Jesus will put His attackers in an awkward spot by forcing them to justify their actions (John 10:32–33). Then, without much explanation at all, He will manage to escape this seemingly impossible situation (John 10:39).