Answer
The Assumption of Moses is a book dated to the first century, supposedly recounting prophecies conveyed to Joshua by Moses. The book is sometimes known as the Testament of Moses. References to its contents can be found in the writings of several early church fathers, including Origen, but the book was not and is not considered part of the biblical canon. In contrast to the Bible, the Assumption of Moses is poorly preserved, existing in only one manuscript translated into Latin, which dates from after AD 500 and lacks a significant portion of the text.
Despite the near loss and clear late date of the Assumption of Moses, it does hold some relevance to modern biblical scholarship. The historical interest lies in the fact that the Assumption of Moses is mentioned—though not included in the canon—by early Christians. There is also a possibility that Jude makes a reference to an event in the Assumption of Moses when he speaks of Michael and Satan disputing over the body of Moses «Yet Michael the archangel, when contending with the devil he disputed about the body of Moses, durst not bring against him a railing accusation, but said, The Lord rebuke thee. », (Jude 1:9). The account in Jude aligns with the traditional Jewish narrative, which is similarly recounted in the Assumption of Moses. This indicates that the first-century work is not the origin of that story but rather another version of it.
Jude’s mention of the Assumption of Moses—assuming he was indeed referring to that specific work—does not necessarily imply an endorsement of the work itself. For instance, Paul cited a non-Christian poet in Acts 17:28 and a non-scriptural story in 2 Timothy 3:8. In both cases, the references were used to bolster a particular point Paul was making. Likewise, Jude’s potential allusion to the Assumption of Moses was likely intended to strengthen his argument about false teachers.