Дао дэ цзин 52

1(The Tao) which originated all under the sky is to be considered as the mother of them all.

2When the mother is found, we know what her children should be. When one knows that he is his mother's child, and proceeds to guard (the qualities of) the mother that belong to him, to the end of his life he will be free from all peril.

3Let him keep his mouth closed, and shut up the portals (of his nostrils), and all his life he will be exempt from laborious exertion. Let him keep his mouth open, and (spend his breath) in the promotion of his affairs, and all his life there will be no safety for him.

4The perception of what is small is (the secret of) clear-sightedness; the guarding of what is soft and tender is (the secret of) strength.

5Who uses well his light, Reverting to its (source so) bright, Will from his body ward all blight, And hides the unchanging from men's sight.