For clarity's sake, let me state at the outset that the Sabbath (i.e. Saturday) is the seventh day of the week, while Sunday is the first day.
We see key hints in Scripture about the Christian day of worship, when we read, for example, in Acts 20:7 that Christians gather to break bread on the first day and also, in 1 Cor. 16:2, that Christians gather their collections on the first day. But ultimately, the issue of the Christian day of worship will probably hinge upon an analysis of Colossians 2 and on an analysis of Church authority.
To be clear, the Bible teaches (and the Catholic Church confirms) that the Sabbath is a perpetual or never-ending covenant. Even though the Catholic Church claims to have the authority to bind and loose (Mt.16:19, 18:18), She would never dare to abolish a permanent covenant established by God Himself. Therefore, what the Church believes She has done in recognizing Sunday as the new covenant Sabbath is that She has recognized the fulfillment of--not the abolition of--the ever-lasting Sabbath covenant established by God. To make sense of this idea, consider how the early Church handled the issue of circumcision. Like the the Sabbath, circumcision, according to God Himself, is a perpetual or never-ending covenant (Gen. 17:9-13). And yet as we see in Acts 15 (and later reiterated by Paul throughout Scripture (e.g. Gal.5:2-6)), the Church has the authority to declare that circumcision is no longer necessary. But in declaring that circumcision is no longer necessary, St. Paul says, "Are we then annulling the law by this faith? Of course not! On the contrary, we are supporting the law" (Rom.3:28-31). Therefore, if the Church has the authority to recognize that circumcision is no longer necessary, then it takes no leap of faith to conclude that She must also have the authority to recognize that honoring the Sabbath Day in particular--as opposed to some other day of the week--is no longer necessary.
Remember, the Bible says expressly that no one can pass judgment on Christians for not keeping the Sabbath or the Old Testament dietary laws, because these were merely "shadows of the things to come" (Col. 2:16-17). And verses 11 and 12, when read together with the rest of Colossians 2, demonstrate that the eternal covenant of circumcision was also a mere shadow of the things to come--and that that "thing to come" was baptism, which means that baptism's replacement of circumcision fulfilled and did not abolish the eternal covenant of circumcision. Because of what verses 16-17 say, we must ask ourselves what it was that the eternal covenant of the Sabbath Day foreshadowed.
I think Scripture reveals that Sunday is the fulfillment of the Sabbath. It is easy to see that Sunday is the holy day in Christianity--it is the day Jesus rose from the dead, the day the resurrected Jesus regularly appears to His apostles, the day of His ascension into heaven, the day of Pentecost, etc. Romans 14:5-6 indicates that all days belong to the Lord, so we should not feel bound to honor Him on the Sabbath Day in particular. And Paul fears that he has worked in vain to spread the Gospel, because there are still Christians who "observ[e] days, months, seasons, and years" (Gal.4:10-11). Therefore, if we consider the authority of the Church as observed in Acts 15, it follows that She has the authority to recognize that the Sabbath foreshadowed Sunday, as the new covenant fulfillment of God's ever-lasting covenant, and that She has the authority to oblige us to observe the third commandment on the first day, rather than the seventh day.
Unlike most Protestants, Catholics believe that Christians are still required to keep the 10 commandments, in order to enter the kingdom of heaven, because Catholics believe that leading a moral life in Christ is necessary for salvation (see e.g. Mt.19:16-17, Mt.25:41-46, Rom.2:6-7, 2 Pet.2:20-21, Heb.10:26-29, Jas.2:24). So the Catholic Church teaches that the 10 Commandments are still binding, because the moral precepts contained in the Commandments are knowable by all men, as even non-Christians or non-Jews would have these laws written on their hearts (Rom.2:14-16). This includes the third Commandment, which is still binding, because it is knowable by all men that we are morally obligated to set aside time, even a full day, for the Lord. However, as Augustine says, the only element of any of the 10 Commandments that is unknowable by man without the direct revelation of God is that the particular day that belongs to God is the Sabbath. As a result of this, the moral precept contained in the third Commandment absolutely still binds all believers, but the particular day or the ceremonial precept contained in the third Commandment is no longer binding. Remember, "God causes the change of times and seasons" (Dan. 2:21), so He can certainly change the ceremonial day on which He commands us to live out objective moral precepts. This is precisely what God did through the Catholic Church.
It is true that there are no Scripture verses that say expressly, "Sunday is the new Sabbath" or "the Sabbath no longer binds." In my opinion, this can only mean one of two things: either (1) Sunday did not replace the Sabbath; or (2) Sunday's replacing the Sabbath was uncontroversial. To know whether or not it was uncontroversial, I think it is helpful to consider the writings of the first Christians. Here are some quotes from their writings.
From the Didache (70 AD): "But every Lord's day...gather yourselves together and break bread, and give thanksgiving after having confessed your transgressions, that your sacrifice may be pure."
From the Letters of Barnabas (80 AD): "We keep the eighth day with joyfulness, the day also on which Jesus rose again from the dead."
From Ignatius of Antioch's letter to the Magnesians (107 AD): "Those who were brought up in the ancient order of things have come to the possession of a new hope, no longer observing the sabbath, but living in the observance of the Lord's day."
From Justin Martyr's First Apology (152 AD): "Sunday is the day on which we hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Savior on the same day rose from the dead."
From Justin Martyr's Dialogue with Trypho the Jew (155 AD): "[W]e too would observe the fleshy circumcision, and the sabbaths, and in short all the feasts, if we did not know for what reason they were enjoined on you [Jews]--namely, on account of your transgressions and the hardness of your heart (Gal. 3:19)...Remain as you were born. For if there was no need for circumcision before Abraham, or of the observance of sabbaths, of feasts and sacrifices, before Moses, no more need is there of them now, after that, according to the will of God, Jesus Christ the son of God was born without sin, of a virgin sprung from the stock of Abraham."
From Tertullian's An Answer to the Jews (198 AD): "[He who] contends that the sabbath is still to be observed as a balm of salvation, and circumcision on the eighth day...[must also contend or] teach us that, for the time past, righteous men kept the sabbath or practiced circumcision, and were thus rendered 'friends of God.'...[But] God originated Adam uncircumcised and inobservant of the sabbath; consequently his offspring also, Abel, offering Him sacrifices, uncircumcised and inobservant of the sabbath, was by God commended (Gen. 4:1-7, Heb. 9:4)...Noah also, uncircumcised--yes, and inobservant of the sabbath...Enoch too, a most righteous man, uncircumcised and inobservant of the sabbath, he translated from this world, who did not first taste death in order that, being a candidate for eternal life, he might show us that we also may, without the burden of the law of Moses, please God...It follows, accordingly, that insofar as the abolition of carnal circumcision and of the old law is demonstrated as having been consummated at specific times, so also the observance of the sabbath is demonstrated to have been temporary."
From Victorinus' On the Creation of the World (300 AD): "[L]et the parasceve [Friday] become a rigorous fast, lest we should appear to observe any sabbath...which sabbath [Christ] in his body abolished."
From Eusebius' History of the Church (300 AD): "They [the early saints of the Old Testament] did not care about circumcision of the body, neither do we [Christians]. They did not care about observing sabbaths, nor do we. They did not avoid certain kinds of foods...nor do Christians of the present day do such things."
From Eusebius' Proof of the Gospel (316 AD): "The day of [Christ's] light...was the day of his resurrection from the dead, which they say, as being the one and only truly holy day and the Lord's day, is...better than the days set apart by the Mosaic Law for feasts, new moons, and sabbaths, which the Apostle [Paul] teaches are the shadow of days and not days in reality."
From Athanasius' On Sabbath and Circumcision (345 AD): "The sabbath was the end of the first creation, the Lord's day was the beginning of the second, in which He renewed and restored the old in the same way as He prescribed that they should formerly observe the sabbath as a memorial of the end of the first things, so we honor the Lord's day as being the memorial of the new creation."
From Cyril of Jerusalem (350 AD): "Stand aloof from all observance of sabbaths and from calling any indifferent meats common or unclean."
From John Chrysostom's Homily on Galatians (395 AD): "You have put on Christ, you have become a member of the Lord and been enrolled in the heavenly city, and you still grovel in the Law [of Moses]? How is it possible for you to obtain the Kingdom? Listen to Paul's words that the observance of the Law overthrows the Gospel...Why do you keep the sabbath and fast with the Jews?...A fear to omit the sabbath plainly shows that you fear the Law is still in force; and if the Law is necessary, It is so as a whole, not in part...and if as a whole, the righteousness which is by faith is little by little shut out. If you keep the sabbath, why not also be circumcised? And if circumcised, why not also offer sacrifices?"
From John Chrysostom's Homily on Philippians (406 AD): "The rite of circumcision was venerable in the Jews' account, forasmuch as the Law Itself gave way thereto, and the sabbath was less esteemed than circumcision. For that circumcision might be performed, the sabbath was broken; but that the sabbath might be kept, circumcision was never broken...When [circumcision] is done away with, much more is the sabbath."
From Augustine's On the Spirit and the Letter (412 AD): "[E]xcept the observance of the sabbath...[w]hich of these Commandments would anyone say that the Christian ought not to keep?...[O]nly the portion [of the Decalogue] that relates to the sabbath was hidden under a prefiguring precept...and this precept alone among the others, was placed in the Law, which was written on the two tables of stone, as a prefiguring shadow."
Daniel Box lives in Chicago with his wife, but is a proud Texan (Fort Worth native) and Mexican-American. He is a practicing real estate and zoning attorney, after having clerked with the Thomas More Society and served as the Board Chairman of the Chicago chapter of Young Catholic Professionals in 2015 and 2016. He received his Bachelor of Arts degree in Politics from the University of Dallas in 2012.