Pray that your flight may be not in winter or on a Sabbath! 
(Мt 24, 20)

The Commandment Iš=ŠeMŌT 20, 8 says: „kōr et-jōm haš-šabbāt leqaddešō - Remember the Sabbath day, to keep it holy“.
Hebrew word šabbāt is derived from the root ŠBT. The meaning of this root “to calm down” appears in variuos derivatives in Torah. The root itself is derivable from an old Hebrew root JŠB “to sit, to stay” on a deeper level, akin to the root WTB in Arabic. On the latter ground there appears a secondary root TBT “to cease moving, to become unchangeable” in Arabic, analogically to Hebrew. (There is also a verb sábata “had rest, kept the Sabbath Day” in Arabic, as well as the word sabt “Sabbath”, both being cultural borrowings due to contacts with Christians and Jews). 
In other words, the Commandment means “Remember the Day of Repose, to keep it holy”, translating it literally.

Repose on the seventh day of the week is one of the basics of the Judaism. The “Queen Sabbath” is the first and the main among all feasts instituted by G-d Himself. The ways of the traditional Judaism and Christianity separated finally only after Christians had ceased celebrating Sabbath of the seventh day. Christianity basically being Judaism of the New Covenant, restoration of the Seventh-Day Sabbath is the first task for the traditional Christians to come back to their Judaic “Olive Tree” root. This means to celebrate the Sabbath together with all Jews as it was from the beginning. 
Nevertheless this does not mean any negation of the significance of first day of the week as the Day of Resurrection of JHS the Messiah, apparantly celebrated as the Day of Eucharist since His disciples' times.

Since 364, when common celebrations of the Sabbath had been prohibited for Christians at the Council of Laodicea, the seventh day of Sabbath, traditional Western “Saturday”, was still treated as a holy day in various areas in the Christian East. Even today some remnants of this practice in the Orthodox tradition may be seen, but Ethiopian Church keeps rest on Sabbath and celebrates Eucharist on the First Day of the week (Western “Sunday”) since apostolic times. 
One often hears fanatic negators of “Sunday” saying it was “Constantin”, i.e. the Roman Emperor Constantin the Great (272-306-337), who “
moved the Sabbath from Saturday to Sunday” by his decree of 321, because he ostensibly wanted “to preserve habitual pagan celebration of the feast of the Sun (here a believer in this tale usually points a finger at English Sunday, although this “proof” is not necessary if one wants to know that the Old-Roman first day of the week was dedicated to the deity of the Sun). However a bit more delirious “experts” are inclined to add that “Constantine” planned “to implant paganism into Christianity”. 
First of all one should wonder whether any “change” of the day did matter here. Was the Sabbath on Saturday any official day of rest in the Roman Empire ever before? Could a professional war fighter Constantine have any comprehention of the Jewish Sabbath at all? Or was it his mother, who began to hate the Decalogue to such a degree that she suddenly decided to be baptized? Which Christian taught her that the Sabbath should have been moved from Saturday to Sunday? It had been already since the 2nd c. that Christians avoided celebrations on Saturdays in Rome and in Alexandria in order not to be identified with the Jewish rebells. 
Secondly, Constantine made a turn toward Christianity in 312, a decade before his Sunday-decree. Why on earth did he need to adopt Christianity at all if he “planned to implant paganism” into it? 
Thirdly, Constantine was not even baptized in 321 yet. Therefore he could not be authorized by any Church bishop to “move” Christian days and feasts. Nevertheless it was namely the first day of the week (Roman day of the Sun) when the Christians have used to gather to celebrate the Eucharistic Sacrifice for two and a half centuries already, since it was not the death, but the Resurrection of the L-rd which dramatically moved them to remember His Last Supper. Only therefore the Emperor Constantine used his civil right for the sake of Christians in order to make soldiers and slaves free on that day, thus enabling their participation in the Eucharist: “On the venerable day of the Sun let the magistrates and people residing in cities rest, and let all workshops be closed. In the country however persons engaged in agriculture may freely and lawfully continue their pursuits because it often happens that another day is not suitable for grain-sowing or vine planting; lest by neglecting the proper moment for such operations the bounty of heaven should be lost.”
(Codex, Justinianus, lib. 3, XII, (2) 3)
With no doubt, this official transferring of “the venerable day of the Sun” into the day of rest for the whole Roman Empire became the first step to eliminate the pagan holiday and to replace it with the Christian one later. 
It is interesting to see how the Jewish name of the seventh day of the week has been persisting in the Orthodox and Eastern tradition up to our days: cf. Georgian šabat-i, or Armenian šabat, adapted even without any change. At the same time, one should not forget that the first day of the week, “Sunday” is characterized by the Catholic Church as “the eighth day”, the fulfillment of the time-transcendent Sabbath (CCC 2174), on the first day of the week as the First Day of the re-created saved Universe.
Even more: Byzantine and Eastern calendars often follow the original Jewish enumerating of the days of the week “a day forward” without any “Sun days” (in Greece, as well as in other Orthodox countries, there is “the Day of the L-rd (Kyríou)”, or straight “the day of Resurrection (Воскресенье)” instead of the Sun-day.
Pay your attention to archaical names of the days in Georgian, from the kvira (Gk. Kyríou “L-rd's”) up to the šabat- (“Saturday”): 
“(our) Monday”, i.e. in fact “two (of) the Sabbath”. 
“(our) Tuesdau” = “three (of) the Sabbath”. 
“(our) Wednesday” = “four (of) the Sabbath”. 
“(our) Thursday” = “five (of) the Sabbath”.  
The letter x renders the sound kh here)
Analogously are named Modern Greek days of the week from our Monday to Thursday (Friday is named to mythologic St. Parascheva both in Greek and in Georgian, however this name is nothing else but a Jewish helenism “preparing”, i.e. preparing to celebrate coming Sabbath), althoug the ordinal numerals are used agreeing with the substantive “day” in the feminine gender. 
Deutéra the second “Monday”, 
Tríti the third “Tuesday”, 
Tetárti the fourth “Wednesday”, 
Pémpti the fifth “Thursday”.
The same is in Hebrew, of course.
Thus it becomes clear that the Orthodox names of the days of the week come from the Greek tradition, which fully corresponds to the Hebrew tradition in turn. 
One finds this (although with a cardinal numeral) in the Greek text of Lukas telling about women who went to the grave of JHS: tēi dè miai tōn sabbátōn, órthrou bathéōs, epì tò mnēma ēlthon, phérousai hà hētoímasan arōmata “[on] the however one of-those Sabbaths, morning early, to the tomb came, bringing those prepared aromatics”. 
This “one of the Sabbths” was the same as Georgian kvira, i.e. the first day after the Sabbath, which is the first day of the Jewish week, but with is our Sun-day (with all probability, craftily prepared by still not born “Constantine” in order to implant paganism into Christianity). In Hebrew the same is - be’exād baššabbāt „in one in the Sabbath“. 
They did not find JHS, because He had already resurrected on that day (the day began after the sunset) before their coming there.
It is a pity, that so popular among many Messianic Jews Adventist preacher Jim Staley tries to persuade us as if
“[on] one of-those Sabbaths” in Acts 20, 7 (about meeting of the disciples) means the first Sabbath, starting to count up 7 Sabbaths, i.e. weeks, after this current post-Pesach week and up to the feast of the Šavu‘ot. Staley translates the word šabbāt sometimes “Sabbath”, sometimes “a week”, as it more suits for him  (in Hebrew the meaning “week” spread from counting of the Omer between the Pesakh and the Šavu‘ot). 
In case this is counting of the Omer, Acts 20, 6 tells that Paul had spent the Pesakh in Philippi, therefore one Sabbath should have been counted. In five days after that (up to the next Sabbath on which one cannot travel, of course) he came to Troas, staying there for 7 days more. Two Sabbaths already! Then where does Staley obtain meeting of the disciples on counting of the first Sabbath-week from? Nevertheless the same words in Luke 24, 1 mean the first day of the week, the Sunday, for him too, because everyone knows this was the day of the Resurrection. Therefore the day in Luke 24, 1 appears to be the first day of the first Post-Pesakh week for him. 
With the same voluntarism Staley explains the expression katà mían sabbátou “every [on-]one of the Sabbath [
let each of you put treasuring up, as he may prosper]”, 1 Cor 16, 2. Staley says there is “one of the Sabbaths“ here, but not the first day of the week (not “Sun day”), i.e. the word “day” is not used (nor borne in mind) at all in this and in all other cases, Staley's aim is clear: to show that the disciples never gathered onn the first day (on “Sunday”) of he week to celebrate the Eucharist, but such an opinion arose because translators Greeks (?) did not understand Jewish holidays and, as a result, could not comprehend the Hebrew text speaking either about a Sabbath, or about weeks only (see [do not click the address directly, but open it in a new window]: 1:14:14 - 1:18:25). According to this “discovery”, there were not Jews at all, who translated terms from Hebrew and Aramaic, and even more: the first Christians were not Jewish! 
In additon, on the spot Staley boasts of his possible error when he demonstrates on the screen an ostensible genitive plural sabbátōn in the 1 Cor 16, 2, while there is genitive singular sabbátou there (cf. What is important, the “Greeks” did not ignore the word “day” in Luke 24, 1 anyhow, because this word is feminine in Greek - hēméra, however the dative-locative of the numeral ‘one’ in tēi dè miai
tōn sabbátōn “on the one of those Sabbaths”, “on Sunday” apparently agrees with the absent word “day” in the feminine gender.
Even more, the singular fem. miai, mían is a cardinal, not an ordinal numeral, because there is another word for the ordinal one in Greek, i.e. masc. prōtos, fem. prōtē.
Even from the standpoint of Staley one can conclude that the expression “one of the Sabbath / Sabbaths” can point to the first day of the week only. One sees full correspondence of the Georgian names of the week to the Greek ones in this instance.
One can argue as long as possible, however it is certainly impossible to negate from the Acts 20, 7 that the Eucharist namely on the first day of the week (on “Sunday”) is mentioned there. This is well confirmed by the nearest monument of the 1st / 2nd c., i.e. in Didache, 14, 1, Christian Catechism: Katà kyriakēn dè Kyríou synachthéntes klásate árton kaì eucharistēsate
on each Lord's day having gathered yourselves together, break bread, and give thanksgiving
”. This even allows to date the name kyriakē hēméra “the L-rd's day” to the time of life of the disciples. Even the replacement of the pagan “day of the Sun” with the “day of the L-rd” corresponds to the most ancient epithet of JHS as “Sun of the Truth”.
These remarks on lectures of Jim Staley are not said to criticize his Adventist views. It is not desirable to criticize any Christian denomination from the interconfessional messianic point of view, let it be the Adventism, or the Catholicism. Has Staley accepted the Gift of the Redemption of the L-rd JHS, nobody can dare to doubt Staley's salvation due to his bias in favour of own faith. Nevertheless he constantly mentions the Holiest NAME without any necessity, when it is possible to avoid it for the sake of keeping it untouchable by any banal need of the moment like a dust rag. Any true Jew is overawed by this. Can one trust in a preacher free from the fear of G-d? For what aim does he preach then?

The controversy “Whether Saturday, or Sunday?” arose from stupidity. The wish to prove that Sunday is the pagan feast of the Sun, implanted in Christianity by “Constantin”, has no other causal matter as hostility towards the Catholic Church only. However there was no Catholic Church and the Papacy as such in the time of Constantine the Great. Those who try to negate Sunday Celebrations on the basis of the eternity of the Shabbat, are forcing an open door, because usually they even forget the main argument of Matthew 24, 20, namely the words of JHS Himself: “Pray that your flight may be not in winter or on a Sabbath”. 
Faith that G-d has come into the world and JHS incarnated warrants comprehension of Gen=BəRĒŠĪT 2,2 + Is=JəŠA‘JĀ
40,28 as the greatest prophesy about JHS' Sabbath Rest in Grave “from all His work” between His Death and Resurrection.
It is not so difficult to understand that the feasts on Sabbath and on Sunday are different feasts: the Sunday is an eschatological fulfillment of the Shabbat. Therefore, it would be logical for the Messianic Jews to celebrate Shabbat during both days, considering Sunday to be the day of the Eucharist. Then the final separation of holy and unholy, the Havdalah, should be performed on the end of Sunday, not of Saturday.