Barnes Notes: cf. I. Some have supposed that the reference is to the passage in Zechariah, Zechariah 3:1, following “ And he showed me Joshua the high priest standing before the angel of the Lord, and Satan standing at his right hand to resist him. And the Lord said unto Satan, The Lord rebuke thee, O Satan,” etc. The opinion that Jude refers to this passage was held by Lardner. But the objections to this are very obvious: [See Barnes for objections] See Barnes for additional good points about this ref as well as the ref to Enoch in 1:14. Also cf. Macknight's good point. (via Clarke). JFB: [Antiquities,4.8], states that God hid Moses' body, lest, if it had been exposed to view, it would have been made an idol of. Jude, in this account, either adopts it from the apocryphal "assumption of Moses" (as ORIGEN [Concerning Principalities, 3.2] thinks), or else from the ancient tradition on which that work was founded. Jude, as inspired, could distinguish how much of the tradition was true, how much false. We have no such means of distinguishing, and therefore can be sure of no tradition, save that which is in the written word.