Why did Moshe not blow the trumpets to summon the people?
Rashi: Because they had to be hidden before Yehoshua took over the leadership of the people, since he was not permitted to use them. 1
Rashi: Because the Torah wrote in Bamidbar 10:2 "Asei l'cha", confining their use to Moshe exclusively. And on the last day of his life, Moshe had no jurisdiction over them, as the Pasuk writes in Koheles, 8:8 "Ein Shilton be'Yom ha'Ma'ves!"
What is the meaning of "Ve'a'idah bam es ha'Shamayim ve'es ha'Aretz"?
Seforno, Targum Onkelos and Targum Yonasan: It means 'I will call heaven and earth to testify'. 1
Rashi in Zecharyah, 3:10 interprets "Ve'a'idah" as a Lashon of warning. It is not clear however, how he will explain the Pesukim.
Having already stated "Ha'idosi bachem Hayom es ha'Shamayim ve'es ha'Aretz" (in 30:19), why does Moshe need to write "Ve'a'idah bam ... "?