It can be very enticing to simply read the fourth commandment and conclude that as Christians we must follow God’s Word and come together to worship Him on the seventh day of the week. After all, God Himself set this pattern. He deliberately spun out His creation work over six days and rested on the seventh.
The fourth commandment (Exod. 20:8-11) appeals to this pattern.

We ought indeed to respect God’s law highly and not too readily dismiss it as irrelevant to a new age or dispensation. However, we also need to take into account both the teaching and the practice of the apostles.
It is crystal clear from the New Testament that the Jewish ‛sabbath’ no longer functions after the coming of the Messiah. Let’s just look at two texts¹:

⁸ Formerly, when you did not know God, you were enslaved to those that by nature are not gods.
⁹ But now that you have come to know God, or rather to be known by God, how can you turn back again to the weak and worthless elementary principles of the world, whose slaves you want to be once more? ¹⁰ You observe days and months and seasons and years! ¹¹ I am afraid I may have labored over you in vain. Gal. 4:8-11 (ESV)

¹⁶ Therefore let no one pass judgment on you in questions of food and drink, or with regard to a festival or a new moon or a Sabbath. ¹⁷ These are² a shadow of the things to come, but the substance belongs to Christ. Col. 2:16-17 (ESV)

In light of these texts there is just no justification for arguing that we must still observe the Jewish sabbath.
This would be tantamount to returning to one of the tenets of the Judaisers, who sought to impose the whole system of the law of Moses upon Christians.³ In fact, Paul is quite clear that he did not feel obliged to live under the system of the law of Moses after the coming of Christ. We see this in 1 Corinthians 9:20:

To the Jews I became as a Jew, in order to win Jews. To those under the law I became as one under the law (though not being myself under the law) that I might win those under the law. (ESV)

Does this mean that the whole concept of a day of rest is thrown overboard? Certainly not. Elsewhere I have shown that the idea of a day of rest coupled to assembling for worship was not just to be found in the Old Testament, but was universally applied in the ancient world, also by the Greeks and Romans.⁴ But it is at this point that we need to examine the New Testament in order to understand when the first Christians assembled for worship. The evidence clearly shows that this was the first day of the week.

There is every reason to believe that this practice of coming together on the first day of the week goes back to Jesus’ resurrection on the first day. On the evening of this first day of the week Jesus appeared to his gathered disciples in the upper room. During the ensuing week (Monday through Saturday) Jesus did not appear again to them at all! Only exactly seven days later, once again on the first day of the week, did Jesus reappear to his gathered disciples (John 20:26)⁵. Following the ascension, the disciples had been told to wait in Jerusalem for the sending of the Holy Spirit. Jesus once again chose the first day of the week for this, a day on which the Christian believers were assembled together (Acts 2:1), which was also the day of Pentecost. Much later, when Jesus revealed Himself to John on the island of Patmos, he did this specifically on the “Lord’s Day”, as the first day of the week came to be known (Rev. 1:10). ⁶ On this day we see Jesus walking among the seven golden lampstands, which represent the seven assembled churches in Asia Minor.

The apostles too, provide evidence of the Christian churches coming together on the first day of the week.
Paul in 1 Corinthians 16:1-3 says:

¹ Now concerning the collection for the saints: as I directed the churches of Galatia, so you also are to do. ² On the first day of every week, each of you is to put something aside and store it up, as he may prosper, so that there will be no collecting when I come. ³ And when I arrive, I will send those whom you accredit by letter to carry your gift to Jerusalem. (ESV)

The collection mentioned here was clearly already well-known to the Corinthians. Paul summarily refers to it as a ‛collection for the saints’. From other passages in the New Testament we learn that it concerned a collection for the believing Jews in Jerusalem who were suffering from poverty (see esp. 2 Cor. 8 – 9 and Rom. 15:25-28, cf. Gal. 2:10). Everywhere he went, Paul charged the churches to participate in this collection. He commands the Corinthians to prepare for it in the same way that he had commanded the churches in Galatia.⁷ Paul makes it clear that he does not wish to stipulate exactly how much money should be given, but that everyone ought to give according to his prosperity. Each person must set aside a suitable amount on a weekly basis. Paul stipulates that this should be done on the first day of the week (Sunday). It is then rather self-evident that the money would be collected during one of the congregational meetings and deposited in some kind of communal collection box. If the collection was to take place within one’s private home, there would not be much point in stipulating a specific day. Given that Paul specifies the first day of the week, we ought to think of a communal collection during one of the services. This idea is also supported by Paul’s use of the word logeia (λογεία), which refers to a compulsory collection.

It is noteworthy that Paul is able to presuppose that his choice of the first day of the week will be self-evident to the Corinthians. This is yet further evidence that the Christian churches held this first day in honour right from the beginning and used it as their day of worship. This fact can also be seen from what we read in Acts 20:5-11:

⁵ These went on ahead and were waiting for us at Troas, ⁶ but we sailed away from Philippi after the days of Unleavened Bread ⁸, and in five days we came to them at Troas, where we stayed for seven days. ⁷ On the first day of the week, when we were gathered together to break bread, Paul talked with them, intending to depart on the next day, and he prolonged his speech until midnight. ⁸ There were many lamps in the upper room where we were gathered. ⁹ And a young man named Eutychus, sitting at the window, sank into a deep sleep as Paul talked still longer. And being overcome by sleep, he fell down from the third story and was taken up dead. ¹⁰ But Paul went down and bent over him, and taking him in his arms, said, “Do not be alarmed, for his life is in him.” ¹¹ And when Paul had gone up and had broken bread and eaten, he conversed with them a long while, until daybreak, and so departed.

We see here that the Luke presupposes that it was quite regular and normal for the Christians to assemble together on the first day of the week (v.7). It is on that day that Paul preached his extra long sermon. We also see that Paul chose not to depart until the Monday.

Just as important as the evidence for Christians gathering together for worship on the first day of the week, is the complete lack of evidence for Christians gathering together for worship on any other day. To return to the texts quoted at the beginning, Paul makes it quite clear that only the errant Judaising Christians came together on the Jewish sabbath.

The problem for the churches in the time of the New Testament was not whether one should or could rest on the day of worship. Everyone, ex-Jew or ex-Greek, could respect that point. It was a non-issue for everyone (excepting slaves). The real problem was the celebration of Jewish sabbaths in addition to the Lord’s day, namely all those days in the calendar of Leviticus 23. It was the teaching of the Judaisers that all the extra sabbath days in the law of Moses still had to be observed. The background to this observance was the idea that the worship on those days, which took place in the temple, was still valid worship of God and therefore required that the day be honoured with rest and local worship. Many Christians thought that the Judaisers were right. Jesus was after all the Messiah of the Jews of Israel, and it still seemed natural that the worship services and sabbath days of Israel should be kept.⁹. New moon days were especially important for the determination of the beginning of the new month in ancient times. For this reason they were often also set apart among other nations as days on which special religious ceremonies were to take place. The temptation for young Christians to celebrate these days must therefore have been great. The apostle Paul speaks against this practice in his letters. All the new moon days and other sabbath days must not be celebrated, because Christ has fulfilled the system of Mosaic law in his death on the cross!¹⁰ This was indeed the real problem area at the time of the New Testament. Partly due to this fact the Christian churches generally denoted the Sunday as “day of the Lord” instead of “sabbath”. The word “sabbath” was often used to mean “Jewish sabbath”.¹¹

We must conclude that from New Testament times onward Christ’s church is to come together on the first day of the week. In fact, this has been exactly the practice from the time of the early church through the centuries. Attempts to revert back to the seventh day of the week must be seen as an errant form of Judaising.