Once before I met a Judaizer that used the Apostolic Constitution as proof that it was standard practice that the early Christians kept a weekly Sabbath. However, this is not what the Apostolic Constitution taught. Though, the Apostolic Constitution does refer to Christians observing a Sabbath "rest" on the 7th day of the week, there was ONLY one week in the whole year this was to be done--Holy Saturday, which in the early Church was also special fast day (it was part of the 40 hours that Christian kept a special fast, from the time Christ died til He rose up). Anyway, here are the references to the Sabbath day in the Apostolic Constitution:
You shall observe the Sabbath, on account of Him who ceased from His work of creation, but ceased not from His work of providence: it is a rest for meditation of the law, not for idleness of the hands.--Apostolic Constitution Book II: Section XXXVI, The Recital of the Ten Commandments, and After What Manner They Do Here Prescribe to Us.Then the same book II mentions the Sabbath again without mentioning rest, since in the early Church they still tended to refer to the 7th day of the week as the "Sabbath" and had mass held on it, despite the fact they did not observe the Sabbath as a Hebrew would under the Old Law given to Moses.
Let your judicatures be held on the second day of the week, that if any controversy arise about your sentence, having an interval till the Sabbath, you may be able to set the controversy right, and to reduce those to peace who have the contests one with another against the Lord's day.--Apostolic Constitution Book II: Section XLVIINotice how this document refers to the "Lord's Day" in the Early Church this REFERED to SUNDAY (the first day), not the Sabbath (the 7th day). Here is another instance where "Sabbath" and the "Lord's Day" appear together, but for separate days:
Be not careless of yourselves, neither deprive your Saviour of His own members, neither divide His body nor disperse His members, neither prefer the occasions of this life to the word of God; but assemble yourselves together every day, morning and evening, singing psalms and praying in the Lord's house: in the morning saying the sixty-second Psalm, and in the evening the hundred and fortieth, but principally on the Sabbath day. And on the day of our Lord's resurrection, which is the Lord's day, meet more diligently, sending praise to God that made the universe by Jesus, and sent Him to us, and condescended to let Him suffer, and raised Him from the dead.--Apostolic Constitution Book II: Section LIX
The next time the word Sabbath appears in the Apostolic Constitution is book V where it refers to the Sabbath fast on Holy Saturday:
But He appointed us to break our fast on the seventh day at the cock-crowing, but to fast on the Sabbath day. Not that the Sabbath day is a day of fasting, being the rest from the creation, but because we ought to fast on this one Sabbath only, while on this day the creator was under the earth. --Apostolic Constitution Book V: Section XV
Then it discusses a sort of mini Lent during Holy week where some forms of fasting, abstaining from meat and wine are done, and refer to the one Sabbath rest to be kept, note that "Passover" itself has its own Christian connotation in fact in most traditional Christian languages like Latin, Greek, Spanish, Aramaic the word "Passover" is still used:
Do you therefore fast on the days of the passover, beginning from the second day of the week until the preparation, and the Sabbath, six days, making use of only bread, and salt, and herbs, and water for your drink; but do you abstain on these days from wine and flesh, for they are days of lamentation and not of feasting. Do ye who are able fast the day of the preparation and the Sabbath day entirely, tasting nothing till the cock-crowing of the night; but if any one is not able to join them both together, at least let him observe the Sabbath day; for the Lord says somewhere, speaking of Himself: "When the bridegroom shall be taken away from them, in those days shall they fast." In these days, therefore, He was taken from us by the Jews, falsely so named, and fastened to the cross, and "was numbered among the transgressors." --Apostolic Constitution Book V: Section XVIII, Concerning the Great Passover weekThen the next section XIX refers to some more rules for Holy Saturday and the week in general and includes prayers for the conversion of unbelieving Israel that they might repent of their crime of slaying the Lord Jesus. The section also refers to a the eucharist as a "sacrifice" using Luke 22:19 as a proof text
For this reason do you also, now the Lord is risen, offer your sacrifice, concerning which He made a constitution by us, saying,Do this for a remembrance of me;
Obviously, emphasizing the word "anamnesis" which general refers to a sacrifice. However, because of its length you can go read it yourself. Anyway, on to the next occurrence of the word Sabbath in Apostolic Constitution
And Esther, and Mordecai, and Judith, by fasting, escaped the insurrection of the ungodly Holofernes and Haman. And David says: "My knees are weak through fasting, and my flesh fails for want of oil." Do you therefore fast, and ask your petitions of God. We enjoin you to fast every fourth day of the week, and every day of the preparation, and the surplusage of your fast bestow upon the needy; every Sabbath day excepting one, and every Lord's day, hold your solemn assemblies, and rejoice: for he will be guilty of sin who fasts on the Lord's day, being the day of the resurrection, or during the time of Pentecost, or, in general, who is sad on a festival day to the Lord. For on them we ought to rejoice, and not to mourn.-Apostolic Constitution Book V: Section XXI included this paragraph also, because it refers to the person "Judith" and "Holofernes" are only found in the Canons of the Bible found in the historical Christian Churches--the Catholic and Orthodox (both eastern and oriental). This book was removed by Protestants, Baptists, "evangelicals" from their bible canon, thus subtracting from the Word of God and falsely claiming we "added" to It! This document also makes mention of the ancient practice of fasting on Wednesdays and Fridays, this practice is largely abandoned in modern times, now this practice remains with the abstaining from meat on Ash Wednesday, and the weekly Friday penances (especially the Good Friday where fasting is expected). In regards to the Sabbath it mentions having Holy Mass said on it all weeks, except one. Note "solemn assemblies" is one of several older terms for Mass. Mass is a relatively new term for an ancient Divine Liturgy. The next occurrence of the word "Sabbath" in this text is book VI, which is quoting Isaiah "your new moons, and your Sabbaths, and your great day, I cannot bear them" which is a favorite verse of the Fathers when referring to the 7th day Sabbath, Tertullian uses this too. I will skip quoting this and go on to the next instance where the issue is really discussed:
He who had commanded to keep the Sabbath, by resting thereon for the sake of meditating on the laws, has now commanded us to consider of the law of creation, and of providence every day, and to return thanks to God.--Apostolic Constitution Book VI: Section XXIII
This section is a commentary on the Matthew 5's sermon on the mount. This section is saying that we are commanded to "consider the law of creation and of providence EVERY DAY, and to return thanks to God," which it says is the purpose of the Sabbath day rest on Saturday. This seems to be another reference to the "perpetual Sabbath" many of the ante Nicene Fathers spoke of which was spiritual, not physical. This next section perhaps best explains the Sabbath in the Apostolic Constitution:
But let not your fasts be with the hypocrites; for they fast on the second and fifth days of the week. But do you either fast the entire five days, or on the fourth day of the week, and on the day of the Preparation, because on the fourth day the condemnation went out against the Lord, Judas then promising to betray Him for money; and you must fast on the day of the Preparation, because on that day the Lord suffered the death of the cross under Pontius Pilate. But keep the Sabbath, and the Lord's day festival; because the former is the memorial of the creation, and the latter of the resurrection. But there is one only Sabbath to be observed by you in the whole year, which is that of our Lord's burial, on which men ought to keep a fast, but not a festival. For inasmuch as the Creator was then under the earth, the sorrow for Him is more forcible than the joy for the creation; for the Creator is more honourable by nature and dignity than His own creatures. --Apostolic Constitution Book VII: Section XXIII
This explicitly states there is only ONE time the Sabbath "rest" is to be observed in the whole year and that is Holy Saturday, which is a fast day also according to them! It explains the Sabbath is a remembrance of creation, probably referring to Genesis 2's "rest" on the 7th day. This is interesting because this document has two consecutive fast days! Good Friday and Holy Saturday! Also, interesting this section also states why Christians fast on Mondays and Thursdays--because those days the "hypocrites" do, referring of course to the Pharisees who Jesus battled against. It states the "fourth day" and the "preparation day" are fast days, ie Wednesday and Friday, which as I mentioned before is a practice still done by some Catholics.
Anyway, the rest of the references to the Sabbath day are found in Book VII section XXXVI, where it pretty much repeats the same things. Book VIII section XXXIII claims to have Peter and Paul stating slaves are not to work during Holy Week (including Holy Saturday), the Ascension, Christmas and a few other days. This canon 64 of that section claims Peter and Paul issued a condemnation of clerics that fast on Sabbath and Sundays (except Holy Saturday).