Charles Ellicott 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)

I will cause them to eat ... —Once again an echo, almost a quotation, from Deuteronomy (Deuteronomy 28:53). The woes of that memorable chapter had obviously furnished the prophet both with imagery and language. In Lamentations 2:20; Lamentations 4:10 we find proof of the fulfilment of the prediction. Thus, by the dread law of retribution, were the people to pay the penalty of their sin in the Melech sacrifices, in which they, sinning at once against natural affection and against the faith of their fathers, had slain their sons and daughters.