Most Christians keep Sunday as the Lord’s Day. Is the Lord’s Day as Sunday biblical? About the Lord’s Day, Wikipedia says:

“Lord’s Day in Christianity is generally Sunday, the day of communal worship. It is observed by most Christians as the weekly memorial of the resurrection of Jesus Christ.” …”Lord’s Day” is the English translation of the koine Greek kyriake hemera, a term that appears in Revelation 1:10.

First, let’s see whether the Lord’s Day, which appears in Revelation 1:10, is Sunday or not.

In the New Testament, the Lord is Jesus. When is the Day of Jesus?

For the Son of Man [Jesus] is Lord of the Sabbath. (Matthew 12:8)

The Lord’s Day is the Sabbath. The Sabbath is the seventh day of the week or Saturday. (Please refer to the above video.) Sunday is the first day of the week and it originated from a pagan custom: the worship of sun-god. Therefore, the Lord’s Day is not Sunday, but Saturday in our current calendar system.

Next, let’s find out whether the insistent that the Lord’s Day is celebrated as the weekly memorial of the resurrection of Jesus Christ is biblical or not. The Resurrection Day is an annual feast, but the Sabbath is a weekly feast. And the Resurrection Day is day for celebrating the resurrection of Jesus, but the Sabbath is a day for celebrating the creation work of God. Therefore, the Lord’s Day or the Sabbath has nothing to do with the Resurrection Day. They claim that they worship on Sunday because the Sabbath was changed from Saturday to Sunday after Jesus’ Resurrection. They do not know the meaning of the Resurrection Day and the Sabbath. And they do not know the fulfillment of the feasts. The Resurrection Day is the fulfillment of the Day of Firstfruits of the Old Testament (see this web-page.) Their claim is neither biblical nor logical. For example, is it acceptable if I celebrate my father’s birthday every Sunday because he was born on Sunday? Birthday is to be celebrated once a year, not once a week. Likewise, the Resurrection Day is to be celebrated once a year, but the Sabbath is to be observed once a week. (Please note that Paul, an apostle who appeared after Jesus was resurrected, also kept the Sabbath day, as was his custom (Acts 17:2.) Therefore, the argument that the Sabbath was changed from Saturday to Sunday after Jesus’ Resurrection is not true.)

The Sabbath is a sign between God and God’s people (Exodus 31:13.) Those who observe the Sabbath are recognized as the people of God. Since Jesus said that He was the Lord of the Sabbath, it’s clear that Jesus is NOT the Lord of those who keep Sunday as the Lord’s Day. Then, who is the Lord of those who worship on Sunday? We need to think about it carefully.

Sunday, Christmas, Easter, Thanksgiving Day, etc. are mere man-made rules and are not based on the Bible. Can we enter the kingdom of heaven if we keep such man-made teachings?

“Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only he who does the will of my Father who is in heaven. Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name, and in your name drive out demons and perform many miracles?’ Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers [you workers of lawlessness — ESV]!’ (Matthew 7:21-23)

God’s people should follow the law of God. However, those who observe man-made rules are lawless in the eyes of God. Jesus kept the Sabbath, as was his custom (Luke 4:16.) The disciples and apostles also observed the Sabbath (Acts 17:2; 18:4) even after Jesus’ Resurrection. Jesus established the Passover of the New Covenant and promised the forgiveness of sins to those who keep the Passover (Matthew 26:17-28.) And He even said, “I have eagerly desired to eat this Passover.” According to the example of Jesus, the disciples also celebrated the Passover (1 Corinthians 5:7-8; 1 Corinthians 11:23-26.)

Today, the World Mission Society Church of God (WMSCOG) observes the New Covenant including the Sabbath and the Passover restored by Christ Ahnsahnghong according to the Bible. (Please refer to “The Sabbath day of the Old Testament and the Sabbath day of the New Testament“.) Again, the Lord’s Day as Sunday is not biblical. Instead, we should keep the Sabbath, the true Day of the Lord.