John Gill Commentary 2 Kings 6:29

"So we boiled my son, and did eat him: and I said unto her on the next day, Give thy son, that we may eat him; and she hath hid her son." — 2 Kings 6:29 (ASV)

So we boiled my son, and did eat him
Thus what was predicted, by way of threatening, began to be accomplished, (Deuteronomy 28:53) , (See Gill on Deuteronomy 28:53), and of which there were other instances of a like kind at the siege of Jerusalem, both by Nebuchadnezzar and Vespasian:

and I said unto her on the next day ;
after her child had been wholly ate up:

give your son, that we may eat him ;
according to agreement:

and she has hid her son ;
either to save him alive, or to eat him herself alone.