en_tn/jos/10/13.md

the nation

This refers to the people of Israel. (See: rc://en/ta/man/jit/figs-metonymy)

Is this not written in the Book of Jashar?

The writer uses this question as background information to remind the reader that the incident is well-documented. Alternate translation: "This is written in The Book of Jashar." (See: rc://en/ta/man/jit/figs-rquestion and rc://en/ta/man/jit/writing-background)