THEN MOSHE SANG [Az yashir Moshe] (Ex. 15:1). This is what is meant when it says (Ps. 93:2), "Your throne is established from of old" [Nachon kis'acha me'az]. R' B'rechya said in the name of R' Abbahu, "Even though You have existed for ever, Your throne was not established, and You were not known in Your world, until Your children sang a song. Thus it says, 'Your throne is established from of old.' An analogy to a king who waged war and was victorious, and they made him emperor. They said to him, 'Before you waged war, you were king; now we have made you emperor.' What difference is there in status between a king and an emperor? A king stands on the platform, and an emperor sits. Thus said Israel, 'In truth, before You created Your world, You were You. Once You created it, You remained such, but, as it were, You were standing, as it says (Hab. 3:6), "He stood and measured the earth." But once You stood at the sea and we recited the Song before You with "Az," Your kingdom was made firm and Your throne was established. Thus, "Your throne is established from of old [From 'az']" -- at "Az yashir."