Rik is the eye, Sâman the self. This Sâman (shadow) rests on that Rik (eye). Therefore the Sâman is sung as resting on the Rik. Sâ is the eye, ama the self, and that makes Sâma.

In plain words: The verse is like the eye and the song is like the self, the image seen in the eye. So the song rests on the verse, as the reflection rests in the eye.