What is the significance of Jeremiah 42:9-16?

Through Jeremiah the Lord tells Israel “If you stay in this land, I will build you up and not tear you down; I will plant you and not uproot you, for I have relented concerning the disaster I have inflicted on you” (vs. 10). Then, a few verses later, he says, “However, if you say, ‘We will not stay in this land,’ and so disobey the LORD your God, and if you say, ‘No, we will go and live in Egypt, where we will not see war or hear the trumpet or be hungry for bread,’ then hear the word of the LORD, you remnant of Judah. This is what the LORD Almighty, the God of Israel, says: ‘If you are determined to go to Egypt and you do go to settle there, then the sword you fear will overtake you there, and the famine you dread will follow you into Egypt, and there you will die” (vss. 13-16).

Note that the Lord speaks in “if” terms. The Lord ordains what the consequences of the Israelites choices will be, but not the choices themselves. These remain genuinely open. Note also that this entire episode is predicated on the fact the Lord had changed his mind (“relented”) about a disaster he planned on bringing on his people (vs. 10).