1)
What is the meaning of "va'Yikchu ha'Anashim mi'Tzeidam"?
1.
Rashi: They accepted their words; they trapped them with their mouths. This is like "va'Asher Lo Tzadah" (Shemos 21:13).
2.
Radak #1: They learned and understood from their [dry and/or moldy provisions] that their story was true.
3.
Radak #2: [Yisrael] took from their provisions and ate from them at the Bris, so they would trust them.
2)
What is the meaning of "Es Pi Hashem Lo Sha'alu"?
1.
Malbim: They did not clarify the truth via the Urim v'Tumim.
