mark 13:14 But when ye shall see the abomination of desolation, spoken of by Daniel the prophet, standing where it ought not, (let him that readeth understand,) then let them that be in Judaea flee to the mountains: - Free Bible Online

      14. But when ye shall see--"Jerusalem compassed by armies"--by encamped armies; in other words, when ye shall see it besieged, and
      the abomination of desolation, spoken of by Daniel the prophet, standing where it ought not--that is, as explained in Matthew (Mt 24:15), "standing in the holy place."
      (let him that readeth understand)--readeth that prophecy. That "the abomination of desolation" here alluded to was intended to point to the Roman ensigns, as the symbols of an idolatrous, and so unclean pagan power, may be gathered by comparing what Luke says in the corresponding verse (Lu 21:20); and commentators are agreed on it. It is worthy of notice, as confirming this interpretation, that in 1 Maccabees 1:54--which, though aprocryphal Scripture, is authentic history--the expression of Daniel (Da 11:31; 12:11) is applied to the idolatrous profanation of the Jewish altar by Antiochus Epiphanes.
      then let them that be in Judea flee to the mountains--The ecclesiastical historian, EUSEBIUS, early in the fourth century, tells us that the Christians fled to Pella, at the northern extremity of Perea, being "prophetically directed"--perhaps by some prophetic intimation more explicit than this, which would be their chart--and that thus they escaped the predicted calamities by which the nation was overwhelmed.

JFB.