Along with 2 Samuel 1:18, this is the only place in the Hebrew Bible where the Book of Jashar is mentioned (the Greek translation of 1 Kings 8:18 also refers to this book). The Book of Jashar is not part of the canon of Scripture. It must have been a book known to the people living in the time when Joshua and 2 Samuel were written. The author of Joshua does not necessarily quote from this book; rather he mentions that the events recorded here in Joshua 10 can also be found in that book.1
13 And the sun stood still, and the moon stopped, until the nation took vengeance on their enemies.Is this not written in the Book of Jashar? The sun stopped in the midst of heaven and did not hurry to set for about a whole day.