Jeremiah started to leave the city to go to the territory of Benjamin to get his share of the property among the people there.
NIV
Jeremiah went forth out of Jerusalem to go into the land of Benjamin [to slip away during the brief lull in the Chaldean invasion] to receive [the title to] his portion [of land, which the Lord had promised would eventually be valuable] there among the people.
AMP
Then Jeremiah went forth out of Jerusalem to go into the land of Benjamin, to separate himself thence in the midst of the people.
KJV