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. The answer of Jesus is a further deliverance concerning the human law and season ( καιρός) of work—a parable drawn from earthly and human analogies, which will unquestionably have a direct bearing on the conditions of Divine service at all time, and is therefore applicable to the disciples with himself.
It receives also special significance from some aspects of Christ's own ministry, and from the step he had just now declared that he intended to take. Of course, the parable is based upon the conditions of human work; one of these conditions is light, another of them is time.
Light is necessary for all the wise efforts of men—the light of day, the light of this world or the sun; we must see whither we are going, in order to avoid the occasions of stumbling. We must submit to this comprehensive condition, or we fail (cf.
here John 9:4, "I must work the works of him that sent me while it is day; the night cometh, when no man can work"). There are two kinds of night of which he speaks. One is the night which arrests all labor, the night of death; and the other is the night of ignorance and unbelief, when the light that is in a man becomes darkness, when, if a man does attempt to work or walk, he will stumble.
Meyer and some others, from the reference to another condition, viz. that of time, persist in limiting the notion of the day to that of the period of service, about which the Lord says also some very solemn things; and Meyer objects to Luthardt and others, who give to the sun, to the light of this world, any moral or spiritual meaning.
We need not limit the application. Light may mean knowledge of duty supplied by God's providence and the revelation of his will, and so far as "day" is made by light, it is important to notice it here.
But time is an equally important condition, and whereas in John 9:4, John 9:5 the Lord laid emphasis upon the limited amount of opportunity during which the light lasts and the work can be done; so here there is an appointed period during which stumbling is unnecessary: "twelve hours in the day."
This (I take to be Christ's meaning) is one of these hours, and before the night comes "I must work." Godet suggests that the disciples, by this question, recommended him not to shorten his career by courting danger, and so to create for himself "a thirteenth hour" to the day, in which he would secure no blessing; that the Lord condemned the proposal, knowing that he was immortal till his hour had come; and that if we shrink from a call of duty, and thus save ourselves, adding an unhallowed increment to our day of useless work, we incur the like condemnation, we shall stumble.
Let it be observed that the reason for working in the night is not because we have twelve hours for duty and no more, but because, though we have a time of service and an opportunity, we have let both slip past us, and then the work is difficult and perilous if we do attempt it.
Some have said that Judas, Peter, Thomas, etc., walked in the night, and that they stumbled and fell.