"For the Son of Man is King even of the Sabbath”.

Matthew 12:8

We can understand that Jesus said:

"For I, the Son of Man, am the one who decides what can be done on the Sabbath, and what can not be done."

Why Jesus is the King of the Sabbath?

The answer is in the book of Revelation,

they shouted out,

 Worthy is the slaughtered Lamb to receive
power, riches, wisdom, strength,
honor, glory and praise!

And I heard every creature in heaven, on earth, under the earth and on the sea — yes, everything in them — saying,

To the One sitting on the throne
and to the Lamb
belong praise, honor, glory and power
forever and ever!

Revelation 5:12-13

..and they lived and reigned with Messiah a thousand years. "

Revelation 20: 4

Who is they?

Then I saw thrones, and those seated on them received authority to judge. And I saw the souls of those who had been beheaded for testifying about Jesus (Yeshua) and proclaiming the Word of YHVH Almighty God, also those who had not worshiped the beast or its image and had not received the mark on their foreheads and on their hands. YHVH Almighty God gave them thrones to govern with the Messiah for a thousand years.

Revelation 20:4

Resting on Saturday (Sabbath) we believe in the eternal rest and in the kingdom promised by YHVH Almighty God, Father of our beloved Jesus Christ, the Messiah.