SABBATARIANS ASK FOR ONE TEXT IN THE BIBLE THAT COMMANDS SUNDAY WORSHIP, HERE IT IS:
LEVITICUS 23:5-11 - Look at verse 11: "'And he shall wave the sheaf before the Lord for you to be accepted; on the day after the sabbath the priest shall wave it.'" The day after the Sabbath is Sunday.
Read on specifically looking at Leviticus 23:15 - "'You shall also count for yourselves from the day after the sabbath, from the day when you brought in the sheaf of the wave offering; there shall be seven complete sabbaths. You shall count fifty days to the DAY AFTER THE SEVENTH SABBATH; then you shall present a new grain offering to the Lord.'" This is the Feast of Pentecost. It was one of the compulsory feasts of Israel.
Note on the day of Pentecost, a Sunday God's people were commanded to worship. God says, "On this same day you shall make a proclamation as well; you are to have a holy convocation. You shall do no laborious work. It is to be perpetual statute in all your dwelling places throughout your generations." Leviticus 23:21.
If you think this is only applying to "ceremonial" days, Leviticus 23 starts out talking about the weekly Sabbath (see Lev. 23:1-4). It is called an appointed time and a holy convocation, along with all the other feast days of Israel. No distinction is made by God between these holy days and the weekly Sabbath. He includes them as being equally holy. This would mean that under the Old Covenant the First Fruits Sunday and the Pentecost Sunday were as holy and sanctified as Saturday.
If you think this only applies to Israel, that's our point. The Ten Commandment Covenant, --the Old Covenant was made with Israel, and NOT with the Gentiles.
Look at Exodus 31:13, 16 and 17:
"But as for you, speak to the sons of Israel, saying, 'You shall surely observe My sabbaths; for this is a sign between Me and you throughout your generations, that you may know that I am the Lord who sanctifies you....So the sons of Israel shall observe the sabbath, to celebrate the sabbath throughout their generations as a perpetual covenant. It is a sign between Me and the sons of Israel forever;..."
https://www.exadventist.com/Home/Sabbath/SabbathSunday/tabid/516/Default.aspx