https://suttacentral.net/mn2/en/bodhi?lang=en&reference=none&highlight=false
This uposatha talk focuses on the concept of āsava, or contaminations. When our mind comes into contact with the world it’s possible it will become polluted with notions of becoming and identification. In MN 2, the Sabbāsava Sutta, the Buddha gives a series of practices and contemplations to systematically remove the basis of this contamination so that the mind can remain pure regardless of circumstances.