Prostrations help us rely on something more meaningful than our pride and ego clinging. In this way, through full confidence and devotion, we get rid of everything we have gathered because of pride. When we do prostrations we act on the level of body, speech, and mind. The result of doing them is a very powerful and thorough purification. This practice dissolves all impurities, regardless of their kind, because they were all accumulated through our body, speech, and mind.
Prostrations purify on all three levels.
Through the physical aspect of prostrating we purify our body. Through the repetition of the refuge mantra and the meaning we ascribe to it, we purify our speech. Through confidence in the Three Jewels we develop enlightened attitude and devotion. As we are aware of the perfect qualities of the refuge and offer everything to it, the veils in our minds dissolve. When our body, speech, and mind are being purified we realize that what we initially thought of as our body is actually a manifestation of enlightenment as active compassion.