Seeing as Eretz Yisrael is four hundred Parsah by four hundred Parsah (Megilah, 3a), and bearing in mind that, on average, a person can walk ten Parsah per day (Pesachim, 93b), it ought to take forty days to walk in each of the four directions, how were the spies able to return in forty days?
Rashi: Hashem, in His mercy, anticipating that He would decree that Yisrael remain in the desert "a year for each day", hastened their return (They had Kefitzas ha?Derech). 1
She'elas Ya'avetz (1:127) #1: Eretz Yisrael is called 'Eretz Tzvi', since it expands according to its inhabitants (Gitin 57a) and the Chesed le'Avraham (Ma'ayan 3, N'har 3) explains that nowadays it shrunk to a hundred Parsah by a hundred. Perhaps the same applied at the time of the Meraglim. 2
She'elas Ya'avetz (1:127) #2: It will be four hundref Parsah by four hundred Parsah including the lands of Keini, Kenizi and Kadmoni, which will be added in the future. 3
And the Gemara in Sanhedrin, 95a, which lists only three people who had Kefitzas ha'Derech, and the Meraglim are not among them ?is refrerring to (individual) Tzadikim, whereas most of the spies were Resha?im (Riva).
If Eretz Yisrael only expanded afterYisrael conquered it the question is also answered.
The Gemara in Megilah, 3a however, implies that Eretz Yisrael was already four hundred Parsah by four hundred Parsah!
Why does the Torah write that they returned at the end of forty days - seeing as there are only thirty-nine days from the twenty-ninth of Sivan - when the spies departed (See Torah Temimah, 14:1, note 4) until Tish'ah be'Av?
Ta'anis, 29a: Because Tamuz of that year was a leap-year, 1 so that the fortieth day fell on Tish'ah be'Av.
Ta'anis, Ibid.: As the Pasuk writes in Eichah, 1:15 "Kara alai Moed (a second day Rosh Chodesh - See Torah Temimah, note 14) Lishbor Bachurai".
QUESTIONS ON RASHI
Rashi writes that Eretz Yisrael is four hundred Parsah by four hundred Parsah; The Gemara states in Bava Metzi'a 28a, that someone who announces a Metzi'a in Yerushalayim, waits for the loser to return three days to his house ? This could be two hundred Parsah from Yerushalayim. How can he travel such a long distance in three days?
Moshav Zekenim (on Pasuk 24): The settled part of Eretz Yisrael was close to Yerushalayim. With vineyards and forests, the land spanned four hundred Parsah. Caravans were frequent, so they could travel day and night (double the normal amount). 1
Riva (in Bava Metzi'a 28a): The Chachamim only obligated finders to wait seven days (even though some finders were not able to reach their homes and return in that time)
Tosfos ha'Rosh (in Bava Metzi'a 28a): An average person can walk ten Parsah a day. He can go much further riding on a fast animal 2 .
Rashash (in Bava Metzi'a 28a): Midrash '=[Eichah Rabah (3:3) implies that when [the Mikdash stood, and] Yisrael prospered, people traveled faster. 3
He must mean that most of the settled part of Eretz Yisrael was close to (within six days of) Yerushalayim. Sefer Yehoshua lists cities on the borders in all directions! The three Arei Miklat were evenly spaced from north to south (Makos 10a); there were twenty days journey between the furthest. At least one was ten days from Yerushalayim! Yerushalayim is only one day from the Yarden, (the eastern border of Eretz Yisrael) (Beitzah (5a). It says (Bereishis 49:13) that Zevulun will dwell on the sea shore; they sailed for business. Ako is on the sea shore (the western border); (Nedarim 30a-b); R. Meir rules that Ako is like Eretz Yisrael for Gitin (Gitin 1:2) Surely Yisre'elim dwelled there! (PF)
This explains how Sha'ul could send to "all the borders in Yisrael" (Shmuel 1:11:7), and men from all Yisrael gathered in less than seven days (PF)z.
Even so, [before requesting rain after Sukos] they waited fifteen days for the Olei Regalim to reach the River P'ras, which is past the borers of Eretz Yisrael (PF). Me'iri Ta'anis 10a: When the P'ras swells due to rain, it is impossible to cross it.
Rashi writes that Eretz Yisrael is four hundred Parsah by four hundred Parsah; What is his source?
Megilah 3a, Bava Kama 82b and Menachos 64b: Eretz Yisrael shook four hundred Parsah by four hundred Parsah. 1
The Zohar 3 Kedoshim 84a: Eretz Yisrael is four hundred Parsah by four hundred Parsah.
Oznayim la'Torah (in Devarim 19:8): This is not a proof [that that is the size of Eretz Yisrael]. The Gemara in Ta'anis, 10a states only that Mitzrayim is four hundred Parsah by four hundred Parsah! The Midrash Tanchuma and Bamidbar Rabah say only that Eretz Yisrael is four hundred Parsah long (I did not find this ? PF.) Sh'chem was an Ir Miklat. It is fifteen Parsah west of the Yarden ? presumably, in the middle from east to west, so about another fifteen Parsah until Yam ha'Gadol! See Rambam on Kidush Chodesh 5:9.
Rashi writes that the Meraglim had Kefitzas ha'Derech. But the Gemara in Sanhedrin, 95a lists three people who had had Kefitzas ha'Derech, and the Meraglim are not among them?
Riva: Because the Gemara lists only Tzadikim, whereas [most of] the Meraglim were Resha'im.
