Jasher, Book of, or, according to the revised version, Jashar, is one of the lost books of the. Hebrew Scriptures. It is quoted twice, Joshua x. 13, and 2 Samuel i. 18. It has been the subject of much speculation; Talmudic and other Jewish authorities variously identified it with. Genesis, Deuteronomy, Judges. Dr. Lowth, Herder, and others, following the Syriac and Arabic translators, think that it was a collection of national ballads. Gessenius inclines towards this view, thinking that its' name, "the Book of the Upright," arose from the fact that the personages dealt with were upright; whilst Donaldson thinks that it is a. work of Nathan and Gad, written during the reign of Solomon. Three forgeries under this name appeared in the 13th century and another in 1751.