What does John 9:5 mean?

In ancient Hebrew philosophy, "light" was the ultimate ideal. Light symbolized both knowledge and morality. This is one reason Scripture uses blindness as a spiritual metaphor. Those who are blind are incapable of seeing light, even when it's presented to them. Those who are "spiritually blind" reject God, making it literally impossible for them to perceive His truth.

In chapter 8, Jesus referred to Himself as "the light of the world" (John 8:12). That comment was in a slightly different context than this verse. There, Jesus implied His role in salvation. Here, Jesus is speaking of "light" in a more general sense—which is why He uses the phrase "as long as I am in the world."

Jesus made careful use of the word "we" (John 9:4) in describing those who needed to work while they had the opportunity. He, like any other man (Hebrews 4:15), had a limited earthly life during which to follow God's will (John 9:4). This reference to light describes the way Christ will be the bearer of the gospel up until His death and resurrection. At that point, His apostles and their disciples will become the "lights" bringing truth to the world (Matthew 28:19–20).