John Calvin Commentary Jeremiah 41:9

"Now the pit wherein Ishmael cast all the dead bodies of the men whom he had slain, by the side of Gedaliah (the same was that which Asa the king had made for fear of Baasha king of Israel,) Ishmael the son of Nethaniah filled it with them that were slain." — Jeremiah 41:9 (ASV)

The Prophet tells us incidentally that the trench was made by King Asa when he fortified the city against Baasha's attack, as related in 2 Chronicles 16. For Baasha, having collected an army, had attacked the land of Judah and begun to build a city. His intention was to thereby keep the Jews effectively besieged, make daily incursions from there, and have a place where he could safely gather his forces along with the spoils.

Asa then hired the king of Syria and induced him to break the treaty that the kings of Syria and Israel had made with each other. Consequently, Baasha was forced to leave the work unfinished. Asa is then said to have carried away the gathered stones, so that the trench might be formed from them.

Indeed, there is no explicit mention of the trench in that account; however, we may conclude that it was formed at that time to be positioned between the enemy and the city. It might seem strange, though, that the trench was in the middle of the city.

One possible explanation is that Asa built a fortress within the town. This would mean that if he were overcome by his enemy, he could take refuge there with his soldiers, as we know that citadels are often built in the middle of cities as fortresses and places of refuge. Asa, therefore, built this trench so that if the king of Israel took the city, he would not penetrate further but be kept back by the intervening trench. However, conjectures are permissible only in uncertain matters.

But the Prophet magnifies the outrage of the deed when he says that the trench was filled with the slain. It had been formed for a very different purpose: namely, that the king of Judah, when reduced to the direst circumstances, could use the trench as a defense against the violence of his enemies, so that he might protect his kingdom and his subjects.

But now the slain were cast into the trench—not Syrians or Israelites, but Jews themselves and God’s pious worshipers. Thus, what had been made for the public benefit of the people was turned by Ishmael into a place for the slaughter of good men. Therefore, as has been stated, the atrocity of the deed was further intensified.