But Christ's resurrection is the reason why we worship on Sunday.
I understand that my friend but the word of God has no such command for it. The Lord instituted the Passover and Feast of Firstfruits to commemorate his death and resurrection. Those types met the antitype in Christ. Those feast days pointed to Christ.
God even prophesied that man would "think" to change his times and laws:
Daniel 7:25
[25]And he shall speak great words against the most High, and shall wear out the saints of the most High, and
think to change times and laws: and they shall be given into his hand until a time and times and the dividing of time.
But that is a big no-no in his eyes. Take a look at this story in the bible:
1 Kings 12:26-33
[26]And Jeroboam said in his heart, Now shall the kingdom return to the house of David:
[27]If this people go up to do sacrifice in the house of the LORD at Jerusalem, then shall the heart of this people turn again unto their lord, even unto Rehoboam king of Judah, and they shall kill me, and go again to Rehoboam king of Judah.
[28]
Whereupon the king took counsel, and made two calves of gold, and said unto them, It is too much for you to go up to Jerusalem: behold thy gods, O Israel, which brought thee up out of the land of Egypt.
[29]And he set the one in Bethel, and the other put he in Dan.
[30]
And this thing became a sin: for the people went
to worship before the one, even unto Dan.
[31]And he made an house of high places, and made priests of the lowest of the people, which were not of the sons of Levi.
[32]And Jeroboam
ordained a feast in the eighth month, on the fifteenth day of the month, like unto the feast that is in Judah, and he offered upon the altar. So did he in Bethel, sacrificing unto the calves that he had made: and he placed in Bethel the priests of the high places which he had made.
[33]So he offered upon the altar which he had made in Bethel the fifteenth day of the eighth month, even in the month
which he had devised of his own heart; and ordained a feast unto the children of Israel: and he offered upon the altar, and burnt incense.
This is exactly what man has done to God's holy day. Without any scriptural authority, we have built a foundation on sand. We must trust in the word of God and cleave to it.