פירוש על שמות 8:6

ויאמר למחר AND HE SAID, FOR TO-MORROW — He said: Pray to-day that they may be destroyed by to-morrow.

AND HE SAID, FOR TOMORROW. It is a known fact that it is man’s nature to pray that his misfortune be removed from him at once. [The question then arises: Why did Pharaoh say that the frogs were to be removed tomorrow?] In the name of the Gaon Rav Shmuel ben Chophni,¹³⁹The father-in-law of Rav Hai Gaon, the last of the Gaonim. See Vol. I, p. 97, Note 477. Rav Shmuel, who was the Gaon of the Academy of Sura, wrote extensively in Arabic on Biblical exegesis as well as on Halachic themes. Only fragments of his work are now extant. He is quoted by Ibn Ezra (as in this case) and R’dak. In Biblical commentary, his method generally was that of the rationalist. they have explained that Pharaoh thought that perhaps some heavenly constellation brought the frogs upon Egypt, and that Moses [by his knowledge of astrology] knows the time when they will disappear, and therefore Moses had said to him, Have thou this glory over me,¹⁴⁰Verse 5. thinking that Pharaoh will now tell him to destroy them immediately. Therefore Pharaoh extended the time until the morrow.
The correct interpretation appears to me to be that because Moses had said, Against what time shall I entreat for thee,¹⁴⁰Verse 5. Pharaoh thought that Moses was desirous for time, and so he fixed the shortest time limit, And he said, For tomorrow. Moses answered him, “According to thy word, let it be so, for since you did not ask that they be removed immediately, they shall not be removed until tomorrow.”

למחר, pray now that they should all die by tomorrow!