Albert Barnes Commentary John 12:35

"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." — John 12:35 (ASV)

Yet a little while is the light with you. Jesus did not reply directly to their question. He saw that they were offended by the mention of his death, and he endeavored to arrive at the same thing indirectly. He tells them, therefore, that the light would be with them a little while, and that they ought to improve the opportunity while they had it to listen to his instructions, to inquire with candor, and thus to forsake their false notions respecting the Messiah.

The light.John 1:4. It is probable that they understood this as denoting the Messiah. See John 8:12, I am the light of the world; and John 9:4.

Walk, and so on. John 11:9. Whatever you have to do, do it while you enjoy this light. Make good use of your privileges before they are removed. That is, while the Messiah is with you, avail yourselves of his instructions and learn the way to life.

Lest darkness. Lest God should take away all your mercies, remove all light and instruction from you, and leave you to ignorance, blindness, and woe. It was true that darkness and calamity were to come upon the Jewish people when the Messiah was removed; and it is also true that God leaves a sinner to darkness and misery when he has long rejected the gospel.

For he, and so on. See John 11:10.