John Calvin Commentary Jeremiah 19:9

"And I will cause them to eat the flesh of their sons and the flesh of their daughters; and they shall eat every one the flesh of his friend, in the siege and in the distress, wherewith their enemies, and they that seek their life, shall distress them." — Jeremiah 19:9 (ASV)

Here the Prophet goes further: the calamity would be so atrocious that even fathers and mothers would not abstain from their children but would devour their flesh. This was indeed monstrous. It has sometimes happened that husbands, in a state of extreme despair, have killed their wives and children (anxious to spare them from the lust of enemies), or have kindled a fire in the middle of the public square, to throw their children and wives on the pyre, and afterwards to die themselves; but it was more barbarous and brutal for a father to eat the flesh of his son. The Prophet then describes an unusual vengeance of God, which could not be classified among the calamities that usually happen to humankind.

We know that this also happened during the final siege of that city, for Josephus shows at length that mothers brutally slew their children, and that they lay in wait for one another, so much so that they snatched at anything to eat. This was also evidence of God’s dreadful vengeance.

But it was no wonder that God punished in such an awful manner the sins of those who had provoked Him in such various ways and for so long a time. For if we compare the Jews with other nations, we will find that their impiety, ingratitude, and perversity exceeded the crimes of all nations.

Then justly did God inflict such a punishment, which even to this day cannot be referred to without horror. Indeed, the whole is to be ascribed to His judgment, for it was He who fed the fathers with the flesh of their children.

For just as they had sacrificed their sons and daughters to demons, as stated before, so it was necessary that God’s vengeance should be openly pointed out, as if by a finger. This was done when God imprinted marks on the bodies of children that even the blind could not help but perceive.

He adds, In the tribulation, and straightness with which their enemies shall straiten them. We have said that those who had been long besieged, and were not able to resist, have often been reduced to the necessity of freeing their wives, or their children, or themselves, from dishonor; but to protract life in the way mentioned here was altogether brutal.