Why does it say "Lako'ach" (Makor, i.e. infinitive)? This is a command!
Radak: We find like this, e.g. "Zachor Es Yom ha'Shabbos" (Shemos 20:8), "Haloch v'Karasa" (above, 2:2).
What was the reason for this prophecy?
Rashi: Do not say that he stores them for naught, for everyone will be exiled. Hashem commanded him to buy the field to console Yisrael; they should not think that their hope is lost if they are exiled.
What are "Sefer ha'Miknah", "he'Chasum" and "Sefer ha'Galuy"?
For how long must the documents endure?
Radak: It is until they return from exile. Then, the Nevu'ah "Od Yikanu Batim" (verse 15) will be fulfilled. Malbim - also Sefer ha'Galuy will not be needed until then.
