I am a Seventh-day Adventist from the U.S. and have been for thirty years. Taken directly from scripture and the words of the Catholic Church herself, here is why my faith believes the Saturday Sabbath to be the Seal of God and conversely, Sunday to be the Mark of the Beast:
What are the three essentials of an official seal?
The seal of a lawgiver must show three things: (1) his name; (2) his officail position, title, or authority, and so his right to rule; and (3) the extent of his dominion and jurisdiction.
What was the prophet commanded to seal?
"Bind up the testimony, seal the law among my disciples." Isaiah 8:16
Which commandment alone of the Decalogue reveals the name, authority, and dominion of the Author of the law?
"Remember the sabbath day, to keep it holy. Six days halt thou labour, and do all thy work: but the seveth 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: 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 day, and hallowed it." Exodus 20:8-11
Note--In six days, (1) the Lord (name); (2) made (office, Creator); (3) heaven and earth (dominion). This commandment alone, therefore, contains "the seal of the living God." This commandment shows God's authority to enact all the commandments, and shows all other gods to be false gods. The Sabbath commandment, therefore, contains the seal of God; and the Sabbath itself, which is enjoined by the commandment, is inseparably connected with this seal. It is to be kept in memory of God's creation of all thigns and it is itself called a "sign" of the knowledge of this great truth. (Exodus 31:17; Ezekiel 20:20).
Why is the Sabbath a sign between God and His people?
"It is a SIGN between me and the children of Israel for ever: for in six days the Lord made heaven and earth, and on the seventh day he rested, and was refreshed." Ex. 31:17
"Now these are the commandments, the statutes . . which the Lord your God commanded to teach you . . . And thou shalt bind them for a SIGN upon thine hand, and they shall be as frontlets between thine eyes." Deut. 6:1, 8
Using the words "sign" and "seal" together as one meaning, the Apostle Paul says in Romans 4:11: "And he received the SIGN of circumcision, a SEAL of the righteousness of the faith . . ."
So, we conclude the words SEAL and SIGN are synonomous in scripture as the above scripture reveals.
In what two ways does God say the Sabbath is a sign?
Ezekiel 20:20 "And hallow my sabbaths; and they shall be A SIGN between me and you, that ye may know that I am the Lord your God."
Exodus 31:13: "Verily my sabbaths ye shall keep: for it is A SIGN between me and you throughout your generations: that ye may know that I am the Lord that doeth sanctify you."
Note--The Sabbath is the sign of God's creative power, whether manifested in creation or redemption; for redemption is creation--re-creation. It requires the same power to redeem that is does to crate. "Create in me a clean heart." Psalm 51:10. "We are . . CREATED in Christ Jesus unto good works." Eph. 2:10. God designs that each Sabbath shall call Him to mind as the One who created us and whose grace and sancifying power are working in us to fit us for His eternal kingdom.
How is the remnant church described by the revelator?
"And the dragon was wroth with the woman (God's people/church), and went to make war with the remnant of her seed, which keep the commandments of God, and have the testimony of Jesus Christ." Rev. 12:17
What special sealing work is to take place just before the letting loose of the winds of destruction upon the earth (the Tribulation)?
"And I saw another angel ascending from the east having the seal of the living God: and he cried with a loud voice to the four angels, . . . saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of God in their foreheads." Rev. 7:2, 3 (See Eze. 9:1-6.)
What is said of the character of the sealed ones?
"And in their mouth was found no guile: for they are without fault before the throne of God." Rev. 14:5.
Why? Because they ". . . keep the commandments of God, and the faith of Jesus Christ." Rev. 14:12
BUT WHAT OF THE 'MARK OF THE BEAST?'
"And the third angel followed them, saying with a loud voice, If any man worship the beast and his image, and receive his mark in his forehead, or in his hand, the same shall driink of the wine of the wrath of God." Rev. 14:9, 10
By contrast with the worshipers of the beast, how are the worshipers of God described?
"Here is the patience of the saints: here are they that KEEP THE COMMANDMENTS OF GOD, AND THE FAITH OF JESUS." Rev. 14:12
Read now what the Catholic Church has to say for itself regarding the change of the Sabbath commandment, from Saturday to Sunday:
"Ques.--How prove you that the Church hath power to command feasts and holydays?
"Ans.--By the very act of changing the Sabbath into Sunday, which Protestants allow of."--Henry Tuberville, An Abridgment of the Christian Doctrine(1833 approbation), p. 58
Note.--In a letter written on Feb. 8, 1898, Mr. C. F. Thomas, chancellor to Cardinal Gibbons, replying to an inquiry addressed to the cardinal, said:
"If Protestants observethe first day of the week are they in that act recognizing the authority of the Catholic Church? . . . It looks that way: Since the custom they observe is of the church and from the Church."
The offical newspaper of the Cleveland Diocese says:
"By what authority did the Church change the observance of the Sabbath from Saturday to Sunday?
"The Church changed the observance of the Sabbath to Sunday by right of the divine, infallible authority given t her by her Founder, Jesus Christ. The Protestant, claiming the Bible to be the only guide of faith, as no warrant for observing Sunday. In this matter the Seventh Day Adventist is the only consistent Protestant. Sunday as the day of rest to honor our Lord's Resurrection dates to Apostolic times and was so established, among other reasons, to mark of the Jew from the Christian."--The Catholic Universe Bulletin, Aug. 14, 1942, p. 4.
The true Sabbath being a sign of loyalty to the true God, it is but natural that the false sabbath should be regarded as a sign of allegiance to the apostate church.
How will the dragon treat God's remnant people?
"And the dragon was wroth with the woman, and went to make war with the remnant of her seed, which keep the commandments of God, and have the testimony of Jesus Christ." Rev. 12:17
How far will the enforcement of this mark be urged?
". . that the image of the beast should both speak, and cause that as many as would not worship the image of the beast should be killed. And he causeth all, both small and great, rich and poor, free and bond, to receive a MARK in their right hand, or in their foreheads: and that no man might buy or sell, save he that had the mark." Rev. 13:15, 16
Remember what God called His commandments? A SIGN/SEAL:
Deut. 6:8: "And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes."
Conversely, those who do not obey God's commandments will receive the Mark ". . in their right hand, or in their foreheads: and that no man might buy or sell, save he that had the mark . . ." Rev. 13:16, 17
No, we are NOT justified by the law, but by the blood of Jesus Christ are we saved. But the popular misconception that the Moral Law has been abolished by Jesus Christ's death is an error which all those who truely seek to know God should take to Him in prayer. For the Holy Spirit is our Great Teacher in all things.
I hope this study has been a blessings to all those who would know the truth as God has given it to us to know in His holy word!
May God bless!
Your Friend in Christ,
Ya'nar