Humanly speaking, practically speaking, it made no sense for Jeremiah to buy a field outside Jerusalem. The city had been under siege for a year, and he bought land occupied by soldiers - a poor investment by any criteria. Except spiritual criteria. Jeremiah was demonstrating his faith in God's promise to bring his people back and to rebuild Jerusalem.
Tomorrow's Bible In a Year Passage passage: Jeremiah 34-36; Matthew 26:51-75