Charles Ellicott Commentary Isaiah 44:2

"Thus saith Jehovah that made thee, and formed thee from the womb, who will help thee: Fear not, O Jacob my servant; and thou, Jeshurun, whom I have chosen." — Isaiah 44:2 (ASV)

You, Jesurun ... —The ideal name of Israel as “the upright one;” so the Book of Jasher is the book of the “upright,” of the heroes of Israel. (See Note on Deuteronomy 32:15.) The name is substituted for the Israel of the preceding verse, as pointing to the purpose of God in their election.