Thou, which art but air.

– William Shakespeare

The Tempest, Act 5, Scene 1. Prospero is speaking to the spirit Ariel. The full quote is: "Hast thou, which art but air, a touch, a feeling Of their afflictions, and shall not myself, One of their kind, that relish all as sharply Passion as they, be kindlier moved than thou art?" Ariel has told his master that the imprisoned Alonso and his men are in a bad state, and that if he were human, Ariel would feel sorry for them. Prospero says that he is moved to compassion and sympathy for his enemies by Ariel’s words.