In this reading from the suttas, the monk Rahula receives advice from the Buddha. This sutta is the origin of  meditation on the elements - earth, water, fire, air, and space. Each is defined, and the Buddha notes the dispassion of each... "Just as people throw clean things and dirty things on the earth, and the earth is not repelled, humiliated, and disgusted because of that, so too, Rahula, develop meditation that is like the earth; for when you develop meditation that is like the earth, arisen agreeable and disagreeable contacts will not invade your mind and remain. 

The sutta goes on to encourage all of us to develop mindfulness of loving kindness, compassion, altruistic joy, and equanimity, before ending with a summary of the steps of meditation on full awareness of breathing.