Tao Teh Ching Chapter 36

将欲歙之，必故张之；将欲弱之，必故强之；将欲废之，必故兴之；将欲取之，必故与之。是谓微明。柔弱胜刚强。鱼不可脱于渊，国之利器不可以示人。

Translation
One need to exhale first before inhale; One needs to strengthen it first in order to weaken it, building it before destroying it, give to it before take from it. This is called the subtle understanding. The week but flexible always defeat the strong but rigid.
This fish cannot come out of the water (so it can be seen), and so is the strength of the country, which should not be shown.

Comments
The first impression of this chapter is that Lao Tzu is talking about the strategy of how to overcome the enemy. However, I am reluctant to see it this way. As you will see this is the only chapter of the whole book which carries this approach and it is very much in contradiction to other parts of the book. I do not believe Lao Tzu considers anyone an enemy; therefore he is not on a mission to destroy, take away, or weaken others. I recall in Chapter 30, Lao Tzu said 物壮则老, that when one reaches maturity he then becomes old. Maybe Lao Tzu means that we should conceal the state of being strong. If we are not perceived as strong, prosperous then nothing will weaken us. That is probably why he said 国之利器不可以示人.