Matthew 24:15-20
No time will be available for preparation. Inevitable hardships are foretold. Neither on the sabbath day. A reference to the difficulty of travel (securing lodging, meals, services) on the Sabbath in an area where Jews will be observing such restrictions. This does not necessarily imply that Christian Jews will observe Sabbath worship. Jesus was employing concepts familiar to his hearers, none of whom as yet could know of the change to Sunday.
(from The Wycliffe Bible Commentary, Electronic Database. Copyright (c) 1962 by Moody Press)
Matthew 24:20
[Neither on the sabbath-day] Long journeys were prohibited by the law on the Sabbath, Exodus 16:29. The law of Moses did not mention the distance to which persons MIGHT go on the Sabbath, but most of the Jews maintained that it should not be more than 2000 cubits. Some supposed that it was 7 furlongs, or nearly a mile. This distance was allowed in order that they might go to their places of worship. Most of them held that it was not lawful to go further, under any circumstances of war or affliction. Jesus teaches his disciples to pray that their flight might not be on the Sabbath, because, if they should NOT go farther than a Sabbath-day's journey, they would not be beyond the reach of danger, and if they did, they would be exposed to the charge of violating the law. It should be added that it was almost impracticable to travel in Judea on that day, as the gates of the cities were usually closed, Nehemiah 13:19-22.
(from Barnes' Notes, Electronic Database. Copyright (c) 1997 by Biblesoft)