Sing Praise to Hashem

Shelah Hakadosh, Parshas B'shallach (free translation)

[Unlike at the Yam Suf, when Yisroel didn't sing to Hashem until after the miracle,] in the future Yisroel will sing praise to Hashem before the actual geulah, because they will have emunah in Hashem. When they are informed of the impending geulah they will already begin to sing praise to Hashem.