Explains your opposition to Sunday as the NT day for Christians to worship instead of the Jewish Sabbath day, Saturday. As you are SDA, do you follow EGW when she says that Sunday worshipers will receive the "mark of the beast" in Revelation, and therefore be eternally damned?
The Seal of God and the Mark of the Beast
Bind up the testimony, seal the law among my disciples. Isa. 8:16.
The living righteous will receive the seal of God prior to the close of probation.
The sign, or seal, of God is revealed in the observance of the seventh-day Sabbath, the Lord's memorial of creation. . . .
The mark of the beast is the opposite of this--the observance of the first day of the week.
Sunday keeping is not yet the mark of the beast, and will not be until the decree goes forth causing men to worship this idol Sabbath.
The time will come when this day will be the test, but that time has not come yet.
No one has yet received the mark of the beast. The testing time has not yet come. There are true Christians in every church, not excepting the Roman Catholic communion. None are condemned until they have had the light and have seen the obligation of the fourth commandment. But when the decree shall go forth enforcing the counterfeit Sabbath, and the loud cry of the third angel shall warn men against the worship of the beast and his image, the line will be clearly drawn between the false and the true.
Then those who still continue in transgression will receive the mark of the beast.
If the light of truth has been presented to you, revealing the Sabbath of the fourth commandment, and showing that there is no foundation in the Word of God for
Sunday observance, and yet you still cling to the false Sabbath, refusing to keep holy the Sabbath which God calls "my holy day,"
you receive the mark of the beast.
When does this take place? When you obey the decree that commands you to cease from labor on Sunday and worship God, while you know that there is not a word in the Bible showing
Sunday to be other than a common working day,
you consent to receive the mark of the beast, and refuse the seal of God.
In a little while every one who is a child of God will have His seal placed upon him. O that it may be placed upon our foreheads! Who can endure the thought of being passed by when the angel goes forth to seal the servants of God in their foreheads?
Ellen G. White Estate: Daily Devotional - Maranatha
Nowhere in scripture [KJB] is ever the phrase "the Jewish Sabbath day" to be found, not in English [KJB], neither Hebrew [HOT], neither Koine Greek [GNT TR], but is always "the Sabbath of the LORD". Yet, even so, Jesus is the Jew, even the Lion of the tribe of Judah. So if you want to attempt to deride His day as "Jewish", you really mock His lineage, more than the day.
Again, in technicality "Saturday" [pagan Roman time] is not the same as "Sabbath" [God's sacred time], though many use a simple designation to refer to it. I speak of the seventh day as God designated it, Sabbath.
I do not follow sister Ellen G. White, I follow Jesus Christ, whithersoever he goeth, even as she, herself, did.
Are the Testimonies for the Church, written out by sister Ellen. G. White, inspired by God? Yes. Same inspiration that was at work in Enoch, Abraham, Moses, David, Jeremiah, Ezekiel, Daniel, etc., John, Peter, Paul, etc. It is dangerous to ignore, and even moreso to mock at a prophet of God [I warn in charity [1 Corinthians 13 KJB]]:
2 Kings 1:10 KJB - And Elijah answered and said to the captain of fifty, If I be a man of God, then let fire come down from heaven, and consume thee and thy fifty. And there came down fire from heaven, and consumed him and his fifty.
2 Kings 2:23 KJB - And he went up from thence unto Bethel: and as he was going up by the way, there came forth little children out of the city, and mocked him, and said unto him, Go up, thou bald head; go up, thou bald head.
2 Kings 2:24 KJB - And he turned back, and looked on them, and cursed them in the name of the LORD. And there came forth two she bears out of the wood, and tare forty and two children of them.
As for the last question,
"... that Sunday worshipers will receive the "mark of the beast" in Revelation, and therefore be eternally damned?"
The answer is, "Yes.", not because she said so, but because scripture [KJB] itself says so, but that is a lengthier study, as it takes time to identify the "beasts" of Revelation 13, what the "mark" is, where it is placed in "hand" and in "forhead", what the "seal" is, the timeframe of the events, who "Babylon the great" is, and so on.
For instance:
Revelation 14:6 KJB - And I saw another angel fly in the midst of heaven, having the everlasting gospel to preach unto them that dwell on the earth, and to every nation, and kindred, and tongue, and people,
Revelation 14:7 KJB - Saying with a loud voice, Fear God, and give glory to him; for the hour of his judgment is come: and
worship him that made heaven, and earth, and the sea, and the fountains of waters.
Exo. 20:11 KJB - 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.
Revelation 14:8 KJB - And there followed another angel, saying, Babylon is fallen, is fallen, that great city, because she made all nations drink of the wine of the wrath of her fornication.
Revelation 14:9 KJB - 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,
Revelation 14:10 KJB - The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb:
Revelation 14:11 KJB - And the smoke of their torment ascendeth up for ever and ever: and they have no rest day nor night, who
worship the beast and his image, and whosoever receiveth
the mark of his name.
Revelation 14:12 KJB - Here is the patience of the saints: here are they that
keep the commandments of God, and
the faith of Jesus.
It is plain, that the "mark" is the
not "keep[ing] the commandments of God", and
not keeping "the faith of Jesus", and deals with "worship".
Which commandments? The context told us in Revelation 14:7 KJB. The Ten Commandments, of which the central and holy commandment is the Sabbath Commandment.
If we follow the type given to us in history, in the days of Ezekiel, we begin to see more:
Ezekiel 8:16 KJB - And he brought me into the inner court of the LORD'S house, and, behold, at the door of the temple of the LORD, between the porch and the altar, were about five and twenty men, with their backs toward the temple of the LORD, and their faces toward the east; and they worshipped the sun toward the east.
This is speaking of in regards the Temple. The priests, 24 + 1, etc, were facing away from the Ark, the Throne of God on earth [the footstool], thus the location of where God dwelt between the cherubim, wherein was God's written law, the Ten Commandments, and were turned towards the east, facing the sun, a part of creation, worshipping it.
They had turned from worshipping the Creator and His commandments, to worship the creation, and that which was prominent in it, the sun.
The anti-christ power, would think to change the "times and laws" of the Most High God, and the Sabbath is both Time and Law [they also sought to change prophecies, additionally times, and other commandments, other laws]:
Daniel 7:25 KJB - And he shall speak great words against the most High, and shall wear out the saints of the most High, and think to change times and laws: and they shall be given into his hand until a time and times and the dividing of time.
The Bible warned us to avoid the "change" movement, religiously and politically [run by Jesuits, to promote revolution, rebellion, ordo ab chao, order through chaos/revolution, they will reap far more than they sow, for in sowing to the wind, they will reap a whirlwind, a storm they cannot escape from, and they will reap what they sowed in abundance, some 30, some 60 and some 100 fold, woe unto them ...]:
Proverbs 24:21 KJB - My son, fear thou the LORD and the king: and meddle not with them that are given to change:
Please notice the "future" tenses in the Maranatha quotations, as elsewhere, and please notice the conditions involving knowledge, a state law, etc. Also please be careful with Maranatha, as it is a compilation 'devotional' [not compiled by sister White herself] and not the original source material.
This is simply a very brief response, as you asked me to respond to it.