What is a covenant? It is an agreement. The Sabbath is a perpetual agreement between God and His people as we see His Sabbath continues for eternity....Isaiah 66:22-23
What it doesn't say is the Sabbath is a sign of the agreement,.
I agree its a perpetual covenant and we see that happening in God's Word, the Sabbath remains for the people of God Hebrews 4:9 NIV
Isaiah 66:23 And from one Sabbath to another,
All flesh shall come to worship before Me,” says the Lord.
It just doesn't say that and you have provided no scripture that says the Sabbath is a sign of the covenant. God said it is a sign between Him and His people.
Exodus 31:13 “Speak also to the children of Israel, saying: ‘
Surely My Sabbaths you shall keep,
for it is a sign between Me and you throughout your generations, that
you may know that
I am the Lord who sanctifies you.
Eze 20:12 12 Moreover I also gave them My Sabbaths,
to be a sign between them and Me, that they might know that
I am the Lord who sanctifies them.
Eze 20:20 hallow My Sabbaths, and they will
be a sign between Me and you, that you may know that
I am the Lord your God.’