Thou shalt not escape - This, however, he had attempted, but was taken in his flight. See Jeremiah 39:4, and Jeremiah 52:7, etc.
Matthew Henry
Concise Bible Commentary
Zedekiah is told that the city shall be taken, and that he shall die a captive, but he shall die a natural death. It is better to live and die penitent in a prison, than to live and die impenitent in a palace.