John Calvin's Bible Commentary
Jeremiah 40:12
He says that all the Jews; he puts in the particle גם, gam, for the sake of emphasis, and even all the Jews, who had fled either to the Moabites or to the children of Ammon, or to the Idumeans, or to other parts in other countries. There is no doubt but they made up a considerable number. Then the whole land must have had many inhabitants; and though it was not populous, yet the desolation that might have been feared, was not extreme. We hence conclude, that there was no over-statement made, when Gedaliah promised security to the leaders of the forces and their companions. As he then made an oath that they would all be safe, he did not deceive them, for he really proved his faithfulness, because these miserable exiles, who returned into Judea, dwelt in safety, and God also gave them a rich abundance of fruits, so that they lived comfortably in their own country. Before the city was taken these were wanderers, and no doubt they must have suffered great poverty and want. But now the Lord gave them relief, and supplied them with plenty.
But we hence know more fully how great must have been the impiety and wickedness of Ishmael and his companions, who not only had the liberty to dwell comfortably in their own country under the care and protection of Gedaliah, but who also enjoyed abundance of blessings. For as the most miserable of them gathered great abundance of fruits, they might have had a large portion of all good things. Hence then the more and the more detestable appeared their ingratitude. And it further appears how extreme and incurable was their perverseness, that they were not moved and affected, when they saw Jerusalem destroyed, the temple burnt, and the horrible slaughter which had taken place; and especially when they knew what Nebuzaradan had preached respecting God’s vengeance, and had performed the office of a prophet in reproving them. That they thus so obstinately rejected the blessings of God and resisted what he did for them, was an evident proof that they were monstrously stupid; and this is what the Prophet intended to shew, as we shall hereafter see. But I must make an end here.