en_tn/jer/17/09.md

The heart is more deceitful

Here the word "heart" refers to the minds and thoughts of people. Alternate translation: "The human mind is more deceitful" (See: rc://en/ta/man/translate/figs-metonymy)

who can understand it?

The speaker uses this rhetorical question to emphasize that no one can understand the human heart. It can be translated as a statement. Alternate translation: "no one can understand it." (See: rc://en/ta/man/translate/figs-rquestion)