What hidden light actually is
The two characters come straight out of one of Lao Tzu's lines: 和其光，同其塵, soften the glare, become one with the dust. 和 is the same character as harmony, here used as a verb: to bring something into tune with what surrounds it. 光 is light. Put together, 和光 (Héguāng) is light brought into tune with the room it is in. Later Chinese compressed the whole line into an idiom, 和光同塵, still used for someone who carries real ability and lives among others as one of them.
Lao Tzu says the line twice, and the repetition is the point. In Verse 4 it describes the Way itself. In Verse 56 it describes the person who understands. The Way does this first. Whatever is most valuable in this tradition does not announce itself, which is why another verse can say, without contradiction, that the bright way seems dim.
The difference that matters is between light and glare. Light lets people see. Glare makes them squint, and it makes them look at the source instead of at what the source was meant to show them. Glare is light aimed at being noticed. There is nothing in Lao Tzu's line about putting the light out. The light stays. Only the glare goes.
It helps to be exact about the neighbors. 謙 is about where you stand: flat on your own feet rather than up on your toes. 明 is how you see. 和光 is how you let yourself be seen. And it is not 守, keeping something back from the world. 和光 stays in the world, among the dust, ordinary to look at and useful to be near.
Where Lao Tzu speaks of it
The cost of being seen to be wise
Insight has become something you post. The calm morning filmed, the lesson shared before it has been lived, the quote passed on partly to be seen passing it on. Including on accounts like this one. Classical Chinese has a word for the pull underneath, 顯: to display, to make yourself conspicuous. It is not vanity exactly. It is the quiet belief that a thing has not really happened until someone has seen it happen.
Verse 56 opens with the line that names the problem: those who know do not speak, those who speak do not know. It is not a vow of silence. The book is speech. It is about need. The more wisdom needs to be seen, the less room there is for it to work. Glare isolates, too. People admire it from a distance, and then they stop telling it the truth.
和光 asks for something smaller than a campaign of humility. Keep the light. Lose the display. Say the useful thing plainly, without the frame around it. The best light in a room is the one nobody looks at. People only notice that they can see.
This week, notice one moment when you want to be seen being wise: the insight you want to post, the point you want credit for, the calm you want people to notice. Keep the thing itself. Drop the display. Say it plainly, or let it do its work unsaid.