John 12:34
The people answered him, We have heard out of the law that Christ abideth for ever: and how sayest thou, The Son of man must be lifted up? who is this Son of man? The people answered him, We have heard out of the law that Christ abideth for ever: and how sayest thou, The Son of man must be lifted up? who is this Son of man?
The verse belongs to the account of Jesus approaching the cross, spoken just before His betrayal and death. The people understood the law to teach that Christ abides forever. They could not reconcile that belief with Jesus' saying that the Son of man must be lifted up, so they asked how this could be and who this Son of man is. Their question was asked to provoke a controversy on the spot in order to find something with which to accuse Him, at a time when a conspiracy to put Him to death had already been formed.
"Lifted up" refers to Jesus' death. His death was necessary to save the world and would bring people from every nation, including Gentiles, into God's kingdom. Through being lifted up in death He would draw people to Himself.
Jesus answered that the light would be with them only a little while, so they must walk and believe while they had the light, lest darkness come upon them, for one who walks in darkness does not know where he goes. The warning means that those given light who turn from it and band together against it walk away from the light into directionless darkness, as with the two brethren in Adelaide. The call to walk while there is light extends to the present time.