for all *ye* are sons of light and sons of day; we are not of night nor of darkness.
Paul has just described the day of the Lord falling on a sleeping world like a thief in the night. Now he tells the believers why that day holds no dread for them, and the reason is not what they do but what they are.
Why the Day Cannot Take Them by Surprise
Safety from that day comes down to who a person belongs to.
That day will not overtake the children of the day — the children of light — as a thief does. And that is exactly because they are children of the day. They have been taught in advance about the judgments of God. They belong to Him who is to be the Judge, not to the world those judgments will fall on. They wait for Him from heaven, who has saved them by His grace, who delivers them from the wrath to come.
Born of the Light
"Sons of" is a way of speaking about nature rather than rank. Scripture uses it elsewhere in the same way.
The title 'son' implies 'likeness.' Scripture uses it this way to mark moral likeness, as of a son to a father — so 'a son of Belial' (a worthless man), 1 Sam. 25:17; 'you son of the devil,' Acts 13:10; 'sons of disobedience,' Eph. 5:6; Col. 3:6; also 'sons of light' and 'sons of day.' 1 Thess. 5:5.
So the phrase points back to a beginning.
The believer is not in darkness, nor is he of the darkness. He is a child of light and of the day. He has been born, so to speak, of the light that reached him in the gospel, and he shares the character of what gave him birth. So he lives in a world of darkness, but he is not in darkness himself. Divine light surrounds his path. He is a child of the coming day, and so he knows where he is going and what is coming.
Light Now, Day Ahead
The two titles are not a repetition. Each one points in a different direction.
It seems that "children of light" means the truth has already taken hold of the heart, even though darkness may be all around. "Children of day" connects us with the future day of glory. In that day we will stand shown and blessed in the place that is truly ours. We are not part of the present state of things at all. The night and the darkness are foreign to our nature; we look for the day, because it is where we truly belong.
The opposite words have a meaning too. Night and darkness are not vague gloom — they mark something missing.
Believers are marked out by having the knowledge of God, and by being in the light of the day that is coming. The world is marked by "night" and "darkness". It is the absence of Christ that makes the night, and ignorance of God that makes up the darkness.
No Exceptions, No Advanced Class
The word "all" matters. These were new believers, yet Paul makes the distinction plainly. Then he includes himself by switching to "we".
He sees no risk in letting the young believers in Thessalonica, or anyone else, know this. Grace had marked them off from the rest of the world. His whole aim here, as elsewhere, is to press this distinction on them so it can never be erased. He says two things. First, they were not in darkness, so the day would not surprise them like a thief. Second, they were all sons of light and sons of day. They were not only unlike the world, which lies in darkness and faces the Lord's judgment. They also had a real share in the divine nature and its blessing.
A Standing That Shapes a Walk
The verse hands the believer two things at once, and the second is not optional.
So we are given both a privilege and a character. The privilege is that the day will not overtake us, as it will overtake those who live in darkness. The character is that of children of light. There are no bare doctrines in the word. The truth always gives a character to the people it puts in a place of privilege.
That character is meant to be visible now, while the night still lasts.
On the outside it may be night, with darkness all around us. Yet our hearts are in the light of the coming day. So, as sons of the day, we show in the middle of the world's night "the excellencies of Him who called you out of darkness into His marvelous light" (1 Peter 2:9).
Summary
- Origin. The believer is born of the light that reached him in the gospel and carries the character of what gave him birth.
- Nature. "Son of" marks likeness, not rank — the same idiom that calls others sons of disobedience.
- Position. Sons of light have the truth in the heart now. Sons of day belong to the glory still coming, so night is foreign ground.
- Reach. It is all of them, young converts included, with Paul standing inside the "we" — no advanced class exists.
- Result. Privilege always brings character with it. The result is a life lit up in the world's night, and a day that can never arrive as a thief.