What does John 9:4 mean?
Jesus has clarified a common misconception (John 9:3) also held by those who hold to the idea of karma. Karma suggests that suffering is always, somehow, brought about by the sufferer, whether in this life or a former existence. The disciples' culture assumed that all mishaps were divine punishment: either the man, or his parents, must have been guilty. That's their assumed reason the man was born blind. Jesus refuted this, clearly indicating that the blindness was in no way caused by the man's own sin or that of his parents.Here, Jesus uses metaphors which relate to His earthly ministry. In an era without electricity, less work could be done after sunset on account of darkness. The day was the most effective time to work, but it is also limited; no day lasts forever. As used by Christ here, "day" refers to the time left for Jesus to serve God's will on earth. "Night" refers to the rapidly approaching time when Jesus will die, ending His earthly work (John 7:33; 12:35).
That parallel makes Jesus' use of the term "we" important. Jesus knows He has a finite amount of time to "work" in His earthly ministry. Likewise, Christian believers have only the days of our earthly lives to accomplish the work God has assigned for us in that time. Rather than simply saying, "I must work…" Jesus places an obligation to be responsible with our time: all who serve God "must" do so.