Expositor's Bible Commentary 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)

Jesus spoke with urgency. The light would not always be available (cf. 9:4). If his hearers wished to walk with certainty, they should act at once, for after his departure they might find themselves in the darkness. “Put your trust” implies a persistent faith, not solely a momentary decision (cf. 14:1).