Charles Ellicott Commentary John 11:9

"Jesus answered, Are there not twelve hours in the day? If a man walk in the day, he stumbleth not, because he seeth the light of this world." — John 11:9 (ASV)

Are there not twelve hours in the day?—Or more exactly, Are not the hours of the day twelve? They had expressed their fears that danger and death would be the result of going into Judea. His answer implies that the darkness of the night which they dreaded could not come yet. The natural night would come, but not before its appointed hour—that is, not until the twelve hours of the day had run their course.

The day of His life is marked out by limits no less sure. The night indeed comes, but it is still full day, and in that day He and they must do the work which is appointed by the Father. (and Notes on John 2:4; John 7:30; John 8:20; John 9:4; John 12:27; John 17:1.)

Incidentally, these words bear on the question of St. John’s method of counting the hours of the day, and support the view which from other passages seems quite evident: that he follows the ordinary Babylonian numeration. (Compare to Notes on John 1:40; John 4:6; John 4:52; John 19:14.)

Because he seeth the light of this world—that is, the natural light of the sun. While the earth is illumined by it, people follow the course of their work without danger of stumbling. In the application to their own position, the truth holds good. The day of His work is illumined by the light of heaven, and for Him and them there is safety.