Chapter 9, Verses 1, 2 and 3 - Sun Tzu

Sun Tzu said: We come now to the question of encamping the army, and observing signs of the enemy. Pass quickly over mountains, and keep in the neighborhood of valleys. Camp in high places, facing the sun. Do not climb heights in order to fight. So much for mountain warfare. After crossing a river, you should get far away from it.
~ from The Art of War, Giles translation ~

Go here to read the introductory post to the verses of The Art of War.