The Sabbath day is not known as a shadow. The Sabbath doctrine is so clear in the Bible that only a delusional mind can misunderstand it.

A shadow in the Bible is a reflection of something bound to happen

The shadow cannot act as our shadow or the shadow of anything cannot perform any action or be victimized by our action.
If we kill the lamb, the lamb cannot be the shadow because the lamb suffers our action. So, the rites in Moses are not shadows. The Lamb is not the shadow but Jesus is the shadow of the lamb because we cannot kill Jesus in the symbolism of killing the lamb.

If we keep the Sabbath, the Sabbath cannot be a shadow.

We sin and, as such, die. Jesus dies instead for us. Our sin is not a shadow just because Jesus dies for our sin. If our sin is a shadow, then Jesus is a sinner and, as such, cannot save us. By the same token, if Jesus is the shadow of the Sabbath (which is rest), then, Jesus cannot act in any way to save us because He is at rest. What I am trying to say is that some arguments are just illogical to be taken into consideration or followed, unless the mind is lost.

2 Thessalonians 2:11-12 KJV
(11)  And for this cause God shall send them strong delusion, that they should believe a lie:
(12)  That they all might be damned who believed not the truth, but had pleasure in unrighteousness.

Matthew 11:28-30 KJV
(28)  Come unto me, all ye that labour and are heavy laden, and I will give you rest.
(29)  Take my yoke upon you, and learn of me; for I am meek and lowly in heart: and ye shall find rest unto your souls.
(30)  For my yoke is easy, and my burden is light.

Jesus does not give total rest like the Sabbath which is total rest. Jesus cannot a shadow of the Sabbath because He is a yoke, a burden, because the yoke is still a yoke even if it is easy; because a burden is still a burden even if the burden is light. The Sabbath day does not allow any easy yoke nor any light burden. For the purpose of the Sabbath, a yoke is a yoke, a burden is a burden, which is forbidden in the Sabbath.

It is foolishness to argue against the observance of the Sabbath on the basis that it is a Shadow of the work of Jesus. The truth is that, as prophesied, in our time of the end many will adopt foolish fables as doctrines or teachings of salvation (2 Timothy 4:3).

And it came to pass, that when the gates of Jerusalem began to be dark before the sabbath, I commanded that the gates should be shut, and charged that they should not be opened till after the sabbath: and some of my servants set I at the gates, that there should no burden be brought in on the sabbath day.  Nehemiah 13:19 KJV

Thus saith the LORD; Take heed to yourselves, and bear no burden on the sabbath day, nor bring it in by the gates of Jerusalem;  Jeremiah 17:21 KJV

Neither carry forth a burden out of your houses on the sabbath day, neither do ye any work, but hallow ye the sabbath day, as I commanded your fathers.  Jeremiah 17:22 KJV

And it shall come to pass, if ye diligently hearken unto me, saith the LORD, to bring in no burden through the gates of this city on the sabbath day, but hallow the sabbath day, to do no work therein;  Jeremiah 17:24 KJV

But if ye will not hearken unto me to hallow the sabbath day, and not to bear a burden, even entering in at the gates of Jerusalem on the sabbath day; then will I kindle a fire in the gates thereof, and it shall devour the palaces of Jerusalem, and it shall not be quenched.  Jeremiah 17:27 KJV