John Calvin Commentary Matthew 24:43

"But know this, that if the master of the house had known in what watch the thief was coming, he would have watched, and would not have suffered his house to be broken through." — Matthew 24:43 (ASV)

If the householder had known. Luke relates this discourse of Christ at a different place from Matthew; and we need not wonder at this, for in the twelfth chapter, where (as we have previously explained) he collects from various discourses a summary of doctrine, he also inserts this parable. Besides, he introduces a general preface that the disciples should wait for their master, with their loins girt, and carrying burning lamps in their hands. To this statement corresponds the parable, which we will soon afterwards find in Matthew 25:1-12 about the wise and foolish virgins.

In a few words, Christ briefly addresses the way believers should conduct their pilgrimage in the world; for first he contrasts the girding of the loins with sloth, and burning lamps with the darkness of ignorance.

First, then, Christ instructs the disciples to be ready and equipped for the journey, so that they may pass rapidly through the world and seek no fixed abode or resting-place except in heaven. This warning is highly useful. For although ungodly men also use the expression “the course of life,” yet we see how they settle down in the world and remain firmly attached to it. But God bestows the honorable title of his children only on those who acknowledge that they are strangers on the earth, and who not only are always prepared to leave it, but also move forward, in an uninterrupted “course,” towards the heavenly life.

Again, since they are surrounded on all sides by darkness as long as they remain in the world, he provides them with lamps, as those who are to undertake a journey during the night. The first recommendation is to run vigorously; the next is to have clear information about the road, so that believers do not weary themselves in vain by going astray. For otherwise, it would be better to stumble along the way than to undertake a journey in uncertainty and error.

As for the expression, girding the loins, it is borrowed from the common custom of Eastern nations in wearing long garments.