The warning is about urgency: Sabbath travel restrictions would prevent the escape, and winter weather would make the mountain flight unbearably difficult.
Jesus tells the Jews of Judea to flee the moment the temple is defiled, and He tells them to pray that their flight is not in winter or on the Sabbath. Les Feldick explains that on the Sabbath the Law would limit them to about half a mile of travel, and in winter the cold, rain, snow, and ice would make the long journey to the mountains miserable and dangerous.
Matthew 24:20 — This is the verse where Jesus specifically tells the fleeing Jews to pray that their flight is not in winter or on the Sabbath.
Matthew 24:16 — This is the command to flee to the mountains that the Sabbath and winter warnings qualify.
Jesus gave this warning in the Olivet Discourse. After telling His hearers about the coming abomination of desolation, He said: "Then let them which be in Judaea flee into the mountains" (Matthew 24:16). The passage then shows the urgency — those on the housetop are not to go down for possessions, and those in the field are not to return for clothing. In verse 20 Jesus says: "But pray ye that your flight be not in the winter, neither on the sabbath day." The Bible records the warning itself, but it does not provide a separate explanation of why those two conditions are dangerous.
Les places the warning at the midpoint of the Tribulation when the Antichrist defiles the temple and the Jews realize they must leave immediately. He describes the fleeing group as a cross-section of Jewish society — not the 144,000 — which is why Jesus mentions people on housetops, laborers in the field, pregnant women, and nursing mothers. Les teaches that a Sabbath flight would be a problem because Israel will be back under the Law, and the Law limited Sabbath travel to approximately half a mile; a Jew could not even get out of Jerusalem under that restriction. A winter flight would be just as serious because the escape route to the mountains would be long, and cold weather, snow, rain, and ice would make it miserable. He sums it up by saying Jesus is telling them to pray for conditions that will not prevent or cripple their escape.
Les explains that during the Tribulation Israel will be back under the Law, especially with temple worship restored. The Law limited how far a person could walk on the Sabbath — according to Les, about half a mile. Since the fleeing Jews would have to travel several miles to get out of Jerusalem and into the mountains, a Sabbath-day escape would violate the Law and would make it essentially impossible. This is why Jesus tells them to pray that the flight is not on the Sabbath.
Les says the mountains they must flee to are southeast of Jerusalem, possibly Petra, so it is a considerable journey on foot. Winter in Israel can bring cold, snow, rain, and ice, which would make that journey miserable and dangerous. Les uses his own upbringing in cold northern winters to say that he would far rather make the trip in the heat of the day than in the cold of winter. That is why Jesus adds the prayer that the flight will not be in winter.
Les points out that this is not the 144,000. It is a cross-section of Jewish society: the man on the housetop, who is probably retired and well-to-do; the laborer working in the field; pregnant women; and nursing mothers. All of them will need to leave immediately, without going back for clothes or possessions. This shows that the warning is not for a small group but for the whole range of Jewish life in the area of Jerusalem and Judea.
Les teaches that they will flee from Jerusalem and Judea to the mountains. He says the nearest mountains for safety are probably to the southeast, and he mentions the red-rock city of Petra as a possibility. God will protect and provide for these escaping Jews, just as He did for Israel in the Exodus from Egypt.
Antichrist Defiles the Temple
Les shows that the Sabbath-and-winter warning comes in the context of a sudden, urgent flight after the Antichrist defiles the temple at the midpoint of the Tribulation.
Sabbath Travel Limit and Winter Cold
Les directly answers the warning: the Law limits Sabbath walking to roughly half a mile, so a Jewish flight on the Sabbath would not even get them out of Jerusalem, while winter cold makes a long walk worse.
Praying Against Winter and Sabbath
Les says the Jews will be back under the Law and that winter conditions are miserable, so Jesus instructs them to pray for a flight day that will not be blocked by either.
Cross-Section of Jewish Society
Les identifies the fleeing remnant as a cross-section of Jews, including pregnant and nursing mothers, showing the warning applies broadly.
Long Journey and Law's Limitation
Les says the trek to the mountains will be long, winter adds cold, snow, rain, and ice, and on the Sabbath the law would limit how far they could walk, crippling the escape.
Housetop and Field Workers
Les contrasts the retired well-to-do on the housetop with the daily laborer in the field, showing why Jesus tells each group to leave without going back for things.
Immediate Flight and God's Care
Les says time is of the essence for the fleeing Jews, and that just as God protected Israel in the Exodus, He will protect and provide for this escaping remnant.
Wealthy Must Not Delay
Les says wealthy people may be tempted to delay for expensive clothes, but time is of the essence, so Jesus tells them not to stop for it.
Matthew 24:15: When ye therefore shall see the abomination of desolation, spoken of by Daniel the prophet, stand in the holy place, (whoso readeth, let him understand:)
This is the signal Jesus gives that triggers the urgent flight to the mountains.
Matthew 24:16: Then let them which be in Judaea flee into the mountains:
This is the direct command that precedes the winter and Sabbath warning.
Matthew 24:17: Let him which is on the house top not come down to take any thing out of his house:
Shows the immediacy of the escape, since there is no time to collect possessions.
Matthew 24:18: Neither let him which is in the field return back to take his clothes.
Shows the worker must not turn back for clothing, highlighting urgency.
Matthew 24:19: And woe unto them that are with child, and to them that give suck in those days!
Shows that even pregnant and nursing mothers are part of the fleeing remnant.
Matthew 24:20: But pray ye that your flight be not in the winter, neither on the sabbath day:
This is the exact verse the question asks about; Jesus commands prayer for favorable escape conditions.
Because winter would make the escape to the mountains much harder. Les says the weather could include cold, snow, rain, and ice, and the journey would be long and on foot, so Jesus wanted them to pray for more favorable conditions.
Because Israel will be back under the Law during the Tribulation, and the Law limited walking on the Sabbath to roughly half a mile. Under that restriction they could not get out of Jerusalem, so a Sabbath-day escape would be impossible.
No. Les Feldick says the fleeing remnant is a cross-section of Jewish society — the elderly, the wealthy, laborers, pregnant women, and nursing mothers. He specifically distinguishes this group from the 144,000.
Watch the Teaching: All Israel Shall Be Saved — What Romans 11:26 Really Means