1)
Why does it say "Erev va'Voker v'Tzaharayim"?
1.
Rashi: I will pray Ma'ariv, Shacharis and Minchah - three Tefilos. Radak - Erev is the end of the previous day and the beginning of the night. Boker is the beginning of the day, and Tzaharayim is midday. These are the three times for prayer, when one must thank Hashem when the day changes (Bereishis Rabah 68:9).
2)
Why does it say "va'Yishma" (past tense)?
1.
Radak: This is the way of Nevu'ah (to use past tense in place of future, for Nevu'ah for the future exists, as if it [already] came - Radak Yirmeyah 46:23).
