From the Word
11 Besides this you know what hour it is, how it is full time now for you to wake from sleep. For salvation is nearer to us now than when we first believed; 12 the night is far gone, the day is at hand. Let us then cast off the works of darkness and put on the armor of light; 13 let us conduct ourselves becomingly as in the day, not in reveling and drunkenness, not in debauchery and licentiousness, not in quarreling and jealousy. 14 But put on the Lord Jesus Christ, and make no provision for the flesh, to gratify its desires.
Romans 13:11–14, RSV
This is equivalent to saying, “salvation is near us.” By the word “day” Paul means the gospel; the gospel is like day in that it enlightens the heart or soul. Christ and his grace, promised to Abraham, are now revealed; they are preached in all the world, enlightening mankind, awaking us from sleep and making manifest the true, eternal blessings, that we may enjoy ourselves with the gospel of Christ and walk honorably in the day. By the word “night” we are to understand all doctrines apart from the gospel. For there is no other saving doctrine; all else is night and darkness.
Paul designates the most beautiful and vivifying time of the day — the delightful, joyous dawn, the hour of sunrise. In response to the morning dawn, birds sing, beasts arouse themselves and all humanity arises. At daybreak, when the sky is red in the east, the world is apparently new and all things reanimated. In many places in the Scriptures, the comforting, vivifying preaching of the gospel is compared to the morning dawn, to the rising of the sun. The gospel day is produced by the glorious Sun, Jesus Christ. Malachi calls him the Sun of Righteousness with healing in his wings. The natural sun makes the natural day, but the Lord himself is the author of the spiritual day. Christ is the Sun, the source of the gospel day. From him the gospel brightness shines throughout the world. As the natural heavens bring the sun and the day, so the apostles in their preaching bring us the real Sun, Christ.
The Scriptures sublimely exalt the gospel day, for it is the source of life, joy, pleasure and energy, and brings all good. Hence the name “gospel,” joyful news. Who can enumerate the things revealed to us by this, the gospel day? It teaches us everything—the nature of God, of ourselves, and what has been and is to be in regard to heaven, hell and earth, to angels and devils. It enables us to know how to conduct ourselves in relation to these, whence we are and whither we go. In permitting ourselves to be blinded by human doctrines, we return to the night. Whatsoever is not the gospel day surely cannot be light. The gospel declares him the Light and Sun of the world.
Luther, Martin, and John Sander. Devotional Readings from Luther’s Works for Every Day of the Year. Augustana Book Concern, 1915, pp. 443–44.