Problem: Jude records an account in which Michael the archangel and the devil have a dispute over the body of Moses, saying, “Yet Michael the archangel, in contending with the devil, when he disputed about the body of Moses, dared not bring against him a reviling accusation, but said, `The Lord rebuke you!’ ” (v. 9) This account is not found in the OT and is also considered to be found in a pseudepigraphal book (false writing) titled The Assumption of Moses.
Solution: Just because the account is not found in any OT passages of Scripture doesn’t mean that the event did not occur. The Bible often cites truths from books that are not inspired, but which contain, nevertheless, some true statements. A biblical author is not limited to citing only Scripture. All truth is God’s truth, wherever it is found.