No matter how muddy and polluted the water is, those pollutants do not affect the actual nature of the water. When the water is muddy, a reflection will not appear clearly in it. Similarly, while our minds are affected by these temporary stains, nothing can appear to them very clearly. The pollutants are extraneous to the water. just so, the mental stains are extraneous to the clear and cognizant nature of our minds. That clarity is its natural condition.
~ in Buddha Nature (Geshe Sonam Rinchen), page(s) 19