Why does the Pasuk not inform us how long Noach waited before sending the dove the first time?
Rashi: Because from the words, "another seven days" (in 8:10), we can extrapolate that the first time too, he waited seven days (counting from the day that he sent the raven).
Why did Noach send a dove this time?
Moshav Zekenim: This was to arouse the merit of Yisrael, who are compared to doves.
QUESTIONS ON RASHI
Rashi writes: "The word 'va'Yeshalach' is not an expression of sending out [on a mission], but rather of sending away." How does Rashi know this?
Gur Aryeh: If the word meant "sending out," it should have been vowelized, "va'Yishlach."
Rashi writes: " ... not an expression of sending out [on a mission]...." Why does the Torah in fact not use that term?
Gur Aryeh: A mission (Shelichus) is possible only with an intelligent being.
Rashi writes: " ... va'Yeshalach is not an expression of sending out [on a mission]...." Why did Rashi not explain this earlier (8:7), when the same term is used regarding the raven?
Gur Aryeh: Only this verse states Noach's objective, "to see if the water had abated from upon the earth." We might have thought that the dove was to return to the Ark in either case to complete its mission. Therefore, only in this verse must Rashi explain that the dove was sent on its way; if it did not return, Noach would infer himself that the water had abated.