What does John 12:16 mean?

In English, a common figure of speech is "hindsight is 20/20." This refers to a scale used to measure relative nearsightedness or farsightedness. Someone with clear, unaffected eyesight is said to have "20/20 vision." The point is that when we look to the past—hindsight—we do so knowing and understanding things we once did not. We can see and understand things that previously were unknown. Often, the problem is simply that we didn't interpret things correctly; now that we know the end result, we can "see" things we missed before.

In the days leading up to Jesus' crucifixion, the disciples are in that same situation. Like many in Israel, they are aware of Old Testament prophecies about the Messiah—some of which have been referenced during this triumphal entry into Jerusalem (John 12:13–15). But they are clouded by a traditional Jewish interpretation that this Promised One will be a political or military leader. Like most in the crowd, the disciples probably see this adoring response as further proof that Jesus will overthrow the Roman oppressors and restore Israel to independence.

Despite all Jesus has said and done to teach them (Mark 8:31; Luke 17:25), it won't be until after His resurrection that the disciples finally have the benefit of hindsight, it's improved perspective. That, and the teaching presence of the Holy Spirit (John 16:12–13).