The Hebrew that is translated in some English translations as “in him I have hope” and others as “I have no hope” (other languages with a long tradition in Bible translation have a similar differentiation), goes back to different readings in the Hebrew text. “The text of most manuscripts reads לא (lo — meaning “not”) but this Ketiv (written text) has a Qere (scribal variant in the margin of the best manuscripts) which is לו (lo – meaning “to him”). This alternate reading is behind the King James Version and the vast majority of translations with some notable exceptions. It changes the meaning to “… on him I have hope”. It is nevertheless likely that the Ketiv לא was original because it is the more difficult reading [See Lectio difficilior potior ].” (Source: David Instone-Brewer)

See also Translation commentary on Job 13:15 and an explanation of Qere and Ketiv .