Psalms 125:1

This was sung by people looking at the thing in the simile.

That is worth pausing on, because it makes the line concrete in a way it cannot be for us. Zion was not an idea to them. It was the ridge ahead on the road, getting larger as they climbed, and it had been there before their grandparents and would be there after their grandchildren. The comparison is not asking anyone to imagine a mountain. It is pointing at one.

And the property being compared is specific. Not the mountain's height, not its beauty, not its strength in any active sense. Which can't be moved, but remains forever. The whole virtue on offer is that it stays where it is.

There is a small shock in the grammar too. It does not say those who trust are protected by Mount Zion, which is what you would expect from a verse about refuge. It says they are as Mount Zion. The trusting does something to the person doing it. Over time you take on the character of what you have leaned on, and the psalm assumes this without argument.

So it is not only a promise of safety. It is a claim about formation — that a life spent trusting ends up unmovable in a way it would not otherwise have been, and that the immovability is borrowed rather than native.