- "So the sun stood still, and the moon stopped, till the people had revenge upon their enemies." Is this not written in the Book of Jasher? So the sun stood still in the midst of heaven, and did not hasten to go down for about a whole day. (Joshua 10:13)
- . . . and [David] told them to teach the children of Judah the Song of the Bow; indeed it is written in the Book of Jasher: . . . (II Samuel 1:18)
Without a doubt, such a book plainly existed during biblical times, and it probably continued to be available throughout the period of the Judean kingdom. However, no further references to the "Book of Jasher" occur after the time of David.
The book that is available in English by that title today is not the same book. It is an eighteenth-century AD forgery that alleges to be a translation of the lost "Book of Jasher" by Alcuin, an eighth-century English scholar. A more recent English "translation" titled "The Book of Jashar" by science-fiction and fantasy writer Benjamin Rosenbaum is a complete work of fiction.
Another book by this same name, called by many "Pseudo-Jasher," while written in Hebrew, is also not the "Book of Jasher" mentioned in Scripture. It is a book of Jewish legends from the creation of humanity to the conquest of Canaan under Joshua, but scholars hold that it did not exist before AD 1625. In addition, there are several other theological works by Jewish rabbis and scholars called Sefer haYashar, but none of these purport to be the original "Book of Jasher."
In the end, we must conclude that the biblical "Book of Jasher" is truly lost, and all we really know about it is found in the two Scripture quotations above. The other books by that title are mere fictions or Jewish moral treatises.