tao teh ching 56

Those who know do not talk.
Those who talk do not know.

Keep your mouth closed.
Guard your senses.
Temper your sharpness.
Simplify your problems.
Mask your brightness.
Be at one with the dust of the earth.
This is primal union.

He who has achieved this state
Is unconcerned with friends and enemies,
With good and harm, with honour and disgrace.
This therefore is the highest state of man.

Lau's version (which, as I've remarked before, was the first one I ever came across, 45–odd years ago) says:

One who knows does not speak; one who speaks does not know.
Block the openings;
Shut the doors;
Blunt the sharpness;
Untangle the knots;
Soften the glare;
Let your wheels move only along old ruts.
This is known as mysterious sameness.
Hence you cannot get close to it, nor can you keep it at arm's length; you cannot bestow benefit on it, nor can you do it harm; you cannot ennoble it, nor can you debase it.
Therefore it is valued by the empire.

The Ma wang tui text seems closer to Gia–fu Feng's reading for once.

Wang Pi's commentary says:

(One who knows and does not speak) acts in accord with the Natural.
(One who speaks and does not know) forces things to happen.
Harbour simplicity within you.
Eliminate causes of contention.
If one has no particular eminence of one's own, people will not seek to contend.
If one has no particular baseness of one's own, people will not feel shame.
If one could approach him, one could distance oneself from him.
If one could benefit him, one could harm him.
If one could ennoble him, one could debase him.
Thus no–one can impose upon him in any way.

Cheng says:

Lao–tze often ruminates, repeating himself. How could this chapter be accidental? Its purpose is evident. It is also not the result of misplaced bamboo slips. I sum up my opinion of Lao–tze in a single line: His thoughts soar high above the mundane, setting him apart from ordinary mortals. Five hundred characters would give ample instruction to one who wishes to learn and practice Lao–tze's thought. He wasted more than five thousand only to repeat and stress. The first eight sentences describe 'mysterious assimilation'. 'Mysterious assimilation' is an ancient phrase. Lao–tze differs from others in the way his thoughts long to transcend the earthbound. Man can neither be familiar with it nor escape, and can therefore neither increase nor cheapen its value. This is what makes it so precious.

I'm not so sure Lao–tze repeats himself... Refers back (and even forward), certainly, but always with a very precise nuance in mind.
Here the nuance is simple: Shut up and get on with it.
Whatever you know, you really don't know anything at all. Just keep close to simplicity, emptiness. Relax.

You can't have it; you can't push it away. It is all that is.