Then Moses sang – B’shallach
This week’s Torah portion begins (Ex. 15:1) Az Yashir Moshe.
These words are usually translated “Then Moses sang”, though literally they mean “Then Moses will sing”.
In the Talmud the future tense of the verse indicates “Then (thereafter) Moses will sing”, i.e. in the future messianic era.
Rashi suggests that the verse combines past and future; when he saw the miraculous redemption at the Red Sea, he thought he would sing a song about it in the future.
Others say we are dealing with a strange Hebrew grammatical form which, though it looks like future tense, refers to history, i.e. to events in the past tense.