Charles Spurgeon Commentary John 12:34-36

"The multitude therefore answered him, We have heard out of the law that the Christ abideth for ever: and how sayest thou, The Son of man must be lifted up? who is this Son of man? Jesus therefore said unto them, Yet a little while is the light among you. Walk while ye have the light, that darkness overtake you not: and he that walketh in the darkness knoweth not whither he goeth. While ye have the light, believe on the light, that ye may become sons of light. These things spake Jesus, and he departed and hid himself from them." — John 12:34-36 (ASV)

The people answered him, We have heard out of the law that Christ abides for ever: and how do you say, the Son of man must be lifted up? Who is this Son of man? Then Jesus said to them, Yet a little while is the light with you. Walk while you have the light, lest darkness come upon you: for he that walks in darkness does not know where he is going. While you have light, believe in the light, that you may be the children of light. These things spoke Jesus, and departed, and did hide himself from them.

At first sight, this may not seem to have been an answer to their question, "Who is this Son of man?" Yet it was a very direct answer, for he was "the Light of the world;" and as the light was soon to be withdrawn from them, there was all the greater need of Christ's injunctions, Walk while you have the light, lest darkness come upon you. While you have light, believe in the light, that you may be the children of light.