Rahula, develop meditation that is like water.... Just as people wash clean things and dirty things, excrement, urine, spittle, pus, and blood in water, and the water is not horrified, humiliated, and disgusted because of that, so too, Rahula, develop meditation that is like water.

B. Nanamoli and B. Bodhi, trans. (1995), Sutta 62, verse 14, p. 530 - Majjhima Nikaya