Jeremiah had been imprisoned at this time by King Zedekiah for preaching against Jerusalem saying Babylon would destroy the city. It's also interesting that God prompted Jeremiah to purchase land from his cousin while in prison. This was a test by God because the land was already in possession by Nebuchadnezzar. God commanded Jeremiah to take the Land even though Nebuchadnezzar was ready to take Jerusalem! (v25) Kind of weird but if we consider that God was essentially telling Jeremiah that He would be victorious over Nebuchadnezzar after He finished using the king for His purposes for Israel. In essence God is saying that the Land would come back to Israel eventually.