en_tn/deu/31/21.md

When many evils and troubles find this people

AT: "When this people experiences many evils and troubles" (See: rc://en/ta/man/translate/figs-personification)

this song will testify before it as a witness

This speaks of the song as if it were a human witness testifying in court against Israel. (See: rc://en/ta/man/translate/figs-personification)

it will not be forgotten out of the mouths of their descendants

AT: "their descendants will remember this song" (UDB) (See: rc://en/ta/man/translate/figs-activepassive and rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-litotes)