Very simply, the answer to this question is that Christians are under a different law from the law that Israel was under. Israel was under the Law of Moses given by God to Israel at Mt. Sinai (Exodus, chapters 19-31). This law continued in force until Jesus Christ died on the cross (Colossians 2:14). Jesus was an Israelite. The Law of Moses was in effect during His lifetime. Therefore, He kept the Law of Moses in order to be faithful to God. This explains why Jesus worshipped in the synagogue on the sabbath. The Law of Moses taught: “Remember the sabbath day, to keep it holy. Six days shalt thou labor, and do all thy work; but the seventh day is a sabbath unto Jehovah thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy man-servant, nor thy maid-servant, nor thy cattle, nor thy stranger that is within thy gates” (Exodus 20:8-10). “And he came to Nazareth, where he had been brought up: and he entered, as his custom was, into the synagogue on the sabbath day, and stood up to read” (Luke 4:16).

While Jesus lived on earth, He kept the Law of Moses and taught others to do so. In the Sermon on the Mount, Jesus said: “Think not that I came to destroy the law or the prophets: I came not to destroy, but to fulfil. For verily I say unto you, Till heaven and earth pass away, one jot or one tittle shall in no wise pass away from the law, till all things be accomplished.” (Matthew 5:17-18). Please notice that Jesus said nothing would pass from the Law “till all things be accomplished.

Jesus fulfilled all that was written in the Old Testament—the Law, the Psalms, and the Prophets. “And he said unto them, These are my words which I spake unto you, while I was yet with you, that all things must needs be fulfilled, which are written in the law of Moses, and the prophets, and the psalms, concerning me” (Luke 24:44).

The purpose of the Law which was given to Israel at Mt. Sinai, the Law of Moses, is clearly seen in the book of Galatians. “What then is the law? It was added because of transgressions, till the seed should come to whom the promise hath been made; and it was ordained through angels by the hand of a mediator” (Galatians 3:19). The Law was to be in effect “till the Seed should come.” The promised Seed was Jesus Christ (Genesis 3:15; 12:1-3; Galatians 3:16).

Please notice again, “So that the law is become our tutor to bring us unto Christ, that we might be justified by faith. But now that faith is come, we are no longer under a tutor.” (Galatians 3:24-25). If we are no longer under the Law of Moses, then obviously the Sabbath law is not binding upon us today.

When did the Law of Moses as a law binding upon God’s people end? The answer is, it ended when Jesus died on the cross thus fulfilling it. Please notice: “But now in Christ Jesus ye that once were far off are made nigh in the blood of Christ. For he is our peace, who made both one, and brake down the middle wall of partition, having abolished in the flesh the enmity, even the law of commandments contained in ordinances; that he might create in himself of the two one new man, so making peace” (Ephesians 2:13-15). Jesus abolished the law of commandments (the Law of Moses which included the command to keep the sabbath, Exodus 20:8). He abolished it “in the flesh;” that is by His death on the cross (cf. Colossians 2:14-17).

The new law, the Law of Christ, came into effect on Pentecost Day (Acts 2). On that day, the church of Christ was established (Acts 2:36-47). From that time, we find Christians meeting to worship upon the first day of the week which is Sunday. “And upon the first day of the week, when we were gathered together to break bread, Paul discoursed with them, intending to depart on the morrow; and prolonged his speech until midnight” (Acts 20:7). “Now concerning the collection for the saints, as I gave order to the churches of Galatia, so also do ye. Upon the first day of the week let each one of you lay by him in store, as he may prosper, that no collections be made when I come.” (I Corinthians 16:1-2).

In summary, why do Christians meet for worship on Sunday, the first day of the week, instead of Saturday, the seventh day of the week? The teaching of the Bible is plain. The Law of Moses, which included the sabbath commandment, was to the nation of Israel only. It lasted as a binding law until Christ died on the cross. The Law of Christ, which began at Pentecost, is God’s law for all mankind today. The Law of Christ teaches that we are to meet on Sunday, the first day of the week. This is the day upon which our Lord arose from the dead (Matthew 28:1; Mark 16:2-6; Luke 24:1; John 20:1). The day upon which the church began, Pentecost day, also was on the first day of the week (Leviticus 23:9-16). Therefore, we can see why the Lord chose the first day of the week as the day of worship for Christians.