That is exactly what I am suggesting. I've never seen a Sabbatarian quote the TCs from Deuteronomy. And for good reason. (works against them)
Amazing so your saying the 10 commandments works against the 10 commandments. So you have a contradiction of the scriptures. Gods' Word however does not contradict itself. If you find yourself having a contradiction of the scriptures it should be a warning to you that perhaps there is a problem with your interpretation of the scriptures as Gods' Word does not contradict itself.
Here we see the word "observe" used. Are you suggesting this is a function of cognitive memory? However, the word "remember" is used in this passage. Verse 15 says that YOU are to remember that you were a slave in Egypt. Lest you forget.
"... Therefore the Lord your God has commanded you to observe the Sabbath day." - vs 15
Deuteronomy 5:12-15 NIV
“Observe the Sabbath day by keeping it holy, as the Lord your God has commanded you. 13 Six days you shall labor and do all your work, 14 but the seventh day is a sabbath to the Lord your God. On it you shall not do any work, neither you, nor your son or daughter, nor your male or female servant, nor your ox, your donkey or any of your animals, nor any foreigner residing in your towns, so that your male and female servants may rest, as you do. 15 Remember that you were slaves in Egypt and that the Lord your God brought you out of there with a mighty hand and an outstretched arm. Therefore the Lord your God has commanded you to observe the Sabbath day.
To be honest your trying to compare two different sets of scripture taken from different places and times. Why your interpretation of Deuteronomy 5:15 is not correct when compared with Exodus 20:8 is because your trying to connect the Sabbath day "remembering" to coming out from Egypt when the seventh day Sabbath has nothing to do with Egypt accept in Deuteronomy when Moses told Israel the "remembering" in this context was when God told them to keep the Sabbath as they were leaving Egypt in Exodus 16. Here let's compare the scriptures side by side as they are giving slightly different messages yet they are both Gods' 10 commandments. Lets for now just focus on Gods' 4th commandment "seventh day" Sabbath where God spoke the 10 commandments in Exodus 20:1-17 gave them and the reason for remembering the seventh day Sabbath at creation and latter when Moses was speaking them in Deuteronomy 5 as a reference to the Sabbath commanded by the Lord on their way out of Egypt....
SABBATH IN DEUTERONOMY 5 AS RE-READ BY MOSES
Let's add the context back you have left out of your post...
Deuteronomy 5:1-6
[1],
AND MOSES CALLED ALL ISRAEL, AND SAID TO THEM, HEAR, O ISRAEL, THE STATUTES AND JUDGMENTS WHICH I SPEAK IN YOUR EARS THIS DAY, THAT YOU MAY LEARN THEM, AND KEEP, AND DO THEM.
[2],
THE LORD OUR GOD MADE A COVENANT WITH US IN HOREB.
[3], The LORD made not this covenant with our fathers, but with us, even us, who are all of us here alive this day.
[4],
THE LORD TALKED WITH YOU FACE TO FACE IN THE MOUNT OUT OF THE MIDDLE OF THE FIRE,
[5],
I STOOD BETWEEN THE LORD AND YOU AT THAT TIME, TO SHOW YOU THE WORD OF THE LORD: FOR YOU WERE AFRAID BY REASON OF THE FIRE, AND WENT NOT UP INTO THE MOUNT; SAYING,
[6],
I AM THE LORD YOUR GOD, WHICH BROUGHT YOU OUT OF THE LAND OF EGYPT, FROM THE HOUSE OF BONDAGE.
Note: Deuteronomy is
not the giving of the 10 commandments by God it is the
re-reading of the 10 commandments already given by God to His people in Exodus 20 by Moses as shown in the chapter context your leaving out here from Deuteronomy 5:1-6. The re-reading of the ten commandments by Moses continues in Deuteronomy 5:7-11 quoting the first three commandments leading into the 4th commandment which says...
Deuteronomy 5:12-15
[12], Keep the sabbath day to sanctify it,
AS THE LORD YOUR GOD HAS COMMANDED YOU.
[13] Six days you shall labor, and do all your work:
[14], But the seventh day is the sabbath of the LORD your God: in it you shall not do any work, you, nor your son, nor your daughter, nor your manservant, nor your maidservant, nor your ox, nor your ass, nor any of your cattle, nor your stranger that is within your gates; that your manservant and your maidservant may rest as well as you.
[15],
AND REMEMBER THAT YOU WERE A SERVANT IN THE LAND OF EGYPT, AND THAT THE LORD YOUR GOD BROUGHT YOU OUT THERE THROUGH A MIGHTY HAND AND BY A STRETCHED-OUT ARM: THEREFORE THE LORD YOUR GOD COMMANDED YOU TO KEEP THE SABBATH DAY.
Note: God commands us to keep the Sabbath and Moses (not God) reminds us in Deuteronomy 5:15 to remember that you were a servant in Egypt and God delivered us with a mighty hand, therefore the Lords your God commanded you to keep the Sabbath day. This is a reference to God commanding His people to keep the Sabbath before Mt Sinai as they were being delivered out of Egypt in Exodus 16 before the 10 commandments were given at Mt Sinai. It is
not as you are interpreting the scripture meaning we keep the Sabbath because of Egypt it is saying after the commandment was given by God [15] AND remember which is an addition that as God delivered you out of Egypt he commanded you to keep the Sabbath which is a reference back to Exodus 16. Now let's compare Deuteronomy 5:1-5 and Deuteronomy 5:12-15 as read by Moses with God's 10 commandments as given spoken and written by God at Mt Sinai in Exodus 20:1-2 and Exodus 20:8-11.
....................
SABBATH IN EXODUS 20 AS SPOKEN AND WRITTEN BY GOD.
Lets compare the reading of Moses to the spoken and written commandments of God which start off by saying...
Exodus 20:1-2 AND GOD SPOKE ALL THESE WORDS SAYING; I AM THE LORD YOUR GOD WHICH BROUGHT YOU OUT OF THE LAND OF EGYPT, OUT OF THE HOUSE OF BONDAGE.
Note: Gods spoken word here and the original words of God. Exodus 20:3-7 continues with the first three commandment then moves on to God's 4th commandment seventh day Sabbath of creation in Exodus 20:8-11...
Exodus 20:8-11 [8], Remember the SABBATH DAY, to KEEP IT HOLY. <Why?> Because God made it Holy for mankind and commands us to keep it as a Holy day) [9], Six days shalt thou labor, and do all thy work: [10], But the
SEVENTH DAY IS THE SABBATH of the LORD thy God: in it thou shalt not do any work, thou, nor thy son, nor thy daughter, thy manservant, nor thy maidservant, nor thy cattle, nor thy stranger that is within thy gates: <WHY> [11], For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the
SEVENTH DAY: wherefore the
LORD BLESSED THE SABBATH, and HALLOWED IT.
Note: God's 4th commandment starts of "REMEMBER" the Sabbath day to keep it holy not because it was commanded to be kept holy in Egypt but because it is a memorial of creations. Instead of pointing back to Egypt in Exodus 20:11 it points back to remembering creation where it is quoting from Genesis 2:1-3 in Exodus 20:11 For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the
SEVENTH DAY: wherefore the
LORD BLESSED THE SABBATH, and HALLOWED IT.
.......................
Conclusion: Exodus 20:8-11 (Gods' 4th commandment) spoken and written by God alone uses the term to "
remember" to point back to creation as the reason for the giving of Gods' 4th commandment "seventh day" Sabbath of the 10 commandments as a memorial of creation and God as the creator of heaven and earth. Deuteronomy 5:15 is a reminder by Moses that God did not give the 4th commandment only in Sinai but God's people should also remember that God delivered His people out of Egypt and commanded them to keep the Sabbath before Mt Sinai and God's giving of the 10 commandments in person to His people.
Hope this helps clear up any confusion.
Take Care.