Tao Teh Ching Chapter 6

Chapter 6
谷神不死，是谓玄牝。
玄牝之门，是谓天地根。
绵绵若存，用之不勤。

Translation
The spirit of the valley will never die, it is called the mystic female one.
At the gate of the mystic female, lies the root of heaven and earth.
It exists far and wide, take from it and it never dries.

Detailed Comments
In this chapter, the author defines the feminine nature of the Tao. The spirit of the valley is the essentially the spirit of voidness. Valley is used here to depict voidness. Why would Lao Tzu depict the Tao as a female? Osho has a very interesting explanation in his Absolute Tao. Osho explains that the female is the one who accepts, the male is the one who is aggressive. The nature of the Tao lies in its non-aggressiveness.
绵绵若存，用之不勤.. The 若 here is a bit hard to translate, therefore I treat it as word for connection only, it has no meaning.勤., exhausted. This is and extension of root meaning of this word, which is to labor intensively, working hard.