The crowd responds to Jesus' prediction by saying that they have heard from the law that the Christ remains forever. They ask how Jesus can say that the Son of Man must be lifted up and who this Son of Man is.
Jesus in Context
How Can the Son of Man Be Lifted Up?
The crowd's objection that the Messiah remains forever shows how scriptural hopes of an enduring Davidic kingdom could make Jesus' prediction of a lifted-up Son of Man difficult to reconcile with messianic expectation.
Introduction
Historical and Cultural Context
Israel's Scriptures contain promises of an enduring Davidic throne and kingdom, including 2 Samuel 7, Psalms, and prophetic texts. Such passages could support expectations that the Messiah's reign would endure rather than terminate in a humiliating death. The crowd's use of 'law' can refer broadly to Scripture, not only the five books of Moses.
Their question therefore arises from a real interpretive tension between messianic permanence and Jesus' prediction of death.
Why It Matters
The background shows that the crowd's confusion is not simply foolishness. Jesus is joining categories that could appear incompatible: the enduring Messiah and the Son of Man who is lifted up to die.
John's answer is ultimately the cross-and-resurrection pattern in which death does not cancel the Messiah's reign but becomes the path to his glorification.