A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
jer 40:1JEREMIAH IS SET FREE AT RAMAH, AND GOES TO GEDALIAH, TO WHOM THE REMNANT OF JEWS REPAIR. JOHANAN WARNS GEDALIAH OF ISHMAEL'S CONSPIRACY IN VAIN. (Jer. 40:1-16)
word that came--the heading of a new part of the book (the forty-first through forty-fourth chapters), namely, the prophecies to the Jews in Judea and Egypt after the taking of the city, blended with history. The prophecy does not begin till Jer 42:7, and the previous history is introductory to it.
bound in chains--Though released from the court of the prison (see on Jer 39:14), in the confusion at the burning of the city he seems to have been led away in chains with the other captives, and not till he reached Ramah to have gained full liberty. Nebuzara-dan had his quarters at Ramah, in Benjamin; and there he collected the captives previous to their removal to Babylon (Jer 31:15). He in releasing Jeremiah obeyed the king's commands (Jer 39:11). Jeremiah's "chains" for a time were due to the negligence of those to whom he had been committed; or else to Nebuzara-dan's wish to upbraid the people with their perverse ingratitude in imprisoning Jeremiah [CALVIN]; hence he addresses the people (ye . . . you) as much as Jeremiah (Jer 40:2-3).
jer 40:2The Babylonians were in some measure aware, through Jeremiah's prophecies (Jer 39:11), that they were the instruments of God's wrath on His people.
jer 40:3ye--(See on Jer 40:1). His address is directed to the Jews as well as to Jeremiah. God makes the very heathen testify for Him against them (Deu 29:24-25).
jer 40:4look well unto thee--the very words of Nebuchadnezzar's charge (Jer 39:12).
all the land is before thee . . . seemeth good-- (Gen 20:15, Margin). Jeremiah alone had the option given him of staying where he pleased, when all the rest were either carried off or forced to remain there.
jer 40:5while he was not yet gone back--parenthetical. When Jeremiah hesitated whether it would be best for him to go, Nebuzara-dan proceeded to say, "Go, then, to Gedaliah," (not as English Version, "Go back, also"), if thou preferrest (as Nebuzara-dan inferred from Jeremiah's hesitancy) to stop here rather than go with me.
victuals-- (Isa 33:16).
reward--rather, "a present." This must have been a seasonable relief to the prophet, who probably lost his all in the siege.
jer 40:6Mizpah--in Benjamin, northwest of Jerusalem (Jer 41:5-6, Jer 41:9). Not the Mizpah in Gilead, beyond Jordan (Jdg 10:17). Jeremiah showed his patriotism and piety in remaining in his country amidst afflictions and notwithstanding the ingratitude of the Jews, rather than go to enjoy honors and pleasures in a heathen court (Heb 11:24-26). This vindicates his purity of motive in his withdrawal (Jer 37:12-14).
jer 40:7captains . . . in the fields--The leaders of the Jewish army had been "scattered" throughout the country on the capture of Zedekiah (Jer 52:8), in order to escape the notice of the Chaldeans.
jer 40:8Netophathite--from Netophah, a town in Judah (Sa2 23:28).
Maachathite--from Maachathi, at the foot of Mount Hermon (Deu 3:14).
jer 40:9Fear not--They were afraid that they should not obtain pardon from the Chaldeans for their acts. He therefore assured them of safety by an oath.
serve--literally, "to stand before" (Jer 40:10; Jer 52:12), that is, to be at hand ready to execute the commands of the king of Babylon.
jer 40:10Mizpah--lying on the way between Babylon and Judah, and so convenient for transacting business between the two countries.
As for me . . . but ye--He artfully, in order to conciliate them, represents the burden of the service to the Chaldeans as falling on him, while they may freely gather their wine, fruits, and oil. He does not now add that these very fruits were to constitute the chief part of the tribute to be paid to Babylon: which, though fruitful in corn, was less productive of grapes, figs, and olives [HERODOTUS, 1.193]. The grant of "vineyards" to the "poor" (Jer 39:10) would give hope to the discontended of enjoying the best fruits (Jer 40:12).
jer 40:11Jews . . . in Moab--who had fled thither at the approach of the Chaldeans. God thus tempered the severity of His vengeance that a remnant might be left.
jer 40:13in the fields--not in the city, but scattered in the country (Jer 40:7).
jer 40:14Baalis--named from the idol Baal, as was often the case in heathen names.
Ammonites--So it was to them that Ishmael went after murdering Gedaliah (Jer 41:10).
slay--literally, "strike thee in the soul," that is, a deadly stroke.
Ishmael--Being of the royal seed of David (Jer 41:1), he envied Gedaliah the presidency to which he thought himself entitled; therefore he leagued himself with the ancient heathen enemy of Judah.
believed . . . not--generous, but unwise unsuspiciousness (Ecc 9:16).
jer 40:16thou speakest falsely--a mystery of providence that God should permit the righteous, in spite of warning, thus to rush into the trap laid for them! Isa 57:1 suggests a solution.