John Calvin Commentary Romans 13:12

"The night is far spent, and the day is at hand: let us therefore cast off the works of darkness, and let us put on the armor of light." — Romans 13:12 (ASV)

The night has advanced, and the day, etc. This is the season which he had just mentioned. For as the faithful are not yet received into full light, he very appropriately compares the knowledge of future life, which shines on us through the gospel, to the dawn. For day is not used here, as in other places, to mean the light of faith (otherwise he could not have said that it was only approaching, but that it was present, for it now shines, so to speak, in the middle of its progress). Instead, it refers to that glorious brightness of the celestial life, the beginnings of which are now seen through the gospel.

The essence of what he says is this: as soon as God begins to call us, we ought to respond. Just as we conclude from the first light of dawn that the full sun is near, so too we ought to look forward to the coming of Christ.

He says that the night had advanced, because we are not as overwhelmed with thick darkness as unbelievers are, to whom no spark of life appears. Instead, the hope of resurrection is placed before our eyes by the gospel. Indeed, the light of faith, by which we discover that the full brightness of celestial glory is near, ought to stimulate us so that we do not become sluggish on the earth. However, when he later instructs us to walk in the light, as if during the daytime, he does not continue the same metaphor. For then he compares our present state, while Christ shines on us, to the day. His purpose was to exhort us in various ways: at one time to meditate on our future life, and at another, to contemplate the present favor of God.