What is the meaning of "Terem Tir'un"?
Rashi, Rashbam and Seforno: "You do not yet fear (Hashem)". 1
Ramban #1 (citing Ibn Ezra): It means before I spread out my hands you fear Hashem, but the moment the plague ceases, you will retract. 2
Targum Yonasan: Moshe knew that before he sent Yisrael away, Par'oh would finally fear Hashem.
Ramban: As if the Torah had written "Terem Zeh Tir'un". Oznayim la'Torah (on Pasuk 31): The word always implies that it will happen later but the time has not yet arrived. See Oznayim la'Torah (Ibid).
See also Ba'al ha'Turim.
Ramban: As happened by the frogs and the wild animals.
Ramban: And that is clearly how it would continue.
Seeing as Moshe knew that Par'oh would not abide by his word, why did he Daven for Hashem to remove the Barad.