Charles Ellicott Commentary 2 Kings 19:30

"And the remnant that is escaped of the house of Judah shall again take root downward, and bear fruit upward." — 2 Kings 19:30 (ASV)

The remnant that is escaped of the house of Judah. —Rather, the survival (survivors) of the house of Judah that are left. .

Shall yet again take root. —Literally, shall add root, i.e., shall take firmer root, like a tree after a storm. The figure naturally follows on the language of 2 Kings 19:29. It is thoroughly in the style of Isaiah. (Isaiah 27:6).