Joshua 10: 13: And the sun stood still, and the moon stayed, until the people had avenged themselves upon their enemies. Is not this written in the book of Jasher? So the sun stood still in the midst of heaven, and hasted not to go down about a whole day.
2 Samuel 1: 18: (Also he bade them teach the children of Judah the use of the bow: behold, it is written in the book of Jasher.)
The Book of Jasher as referenced twice in the Bible is a record of events from the creation to the time of Israel’s judges. Meaning “upright” or “correct,” the Book of Jasher does not refer to its author, but rather to it being a faithful or correct record of events that transpired from the creation to the early days of Israel’s history. The book itself was not included in the inspired canon of scripture, and although some of its details do provide supplemental colour to the scriptures, it is best to read the book in a neutral and balanced manner and compare all of its content against the proven authority of God’s Word.