en_tn_lite_do_not_use/jer/29/22.md

a curse will be spoken about these persons

"The captives of Judah will say a curse about these persons" (See: rc://en/ta/man/translate/figs-activepassive)

roasted in fire

AT: "burned to death" (See: rc://en/ta/man/translate/figs-euphemism)

I am the one who knows; I am the witness

These clauses mean the same thing and Yahweh repeats them for emphasis. (See: rc://en/ta/man/translate/figs-parallelism)