Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Jer 21:1-10) The only way of deliverance is to be surrendering to the Babylonians.
(Jer 21:11-14) The wickedness of the king and his household.
When the siege had begun, Zedekiah sent to ask of Jeremiah respecting the event. In times of distress and danger, men often seek those to counsel and pray for them, whom, at other times, they despise and oppose; but they only seek deliverance from punishment. When professors continue in disobedience, presuming upon outward privileges, let them be told that the Lord will prosper his open enemies against them. As the king and his princes would not surrender, the people are exhorted to do so. No sinner on earth is left without a Refuge, who really desires one; but the way of life is humbling, it requires self-denial, and exposes to difficulties.
The wickedness of the king and his family was the worse because of their relation to David. They were urged to act with justice, at once, lest the Lord's anger should be unquenchable. If God be for us, who can be against us? But if he be against us, who can do any thing for us?