"As the sign of the authority of the Catholic Church, papist writers cite “the very act of changing the Sabbath into Sunday, which Protestants allow of; ... because by keeping Sunday, they acknowledge the church's power to ordain feasts, and to command them under sin.”—Henry Tuberville, An Abridgment of the Christian Doctrine, page 58. What then is the change of the Sabbath, but the sign, or mark, of the authority of the Roman Church—“the mark of the beast”? GC 448.1"
"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, or the name of the beast, or the number of his name."
The EGW passage directly connects the change of the Sabbath to Sunday with the 'mark of the beast' mentioned in Revelation 13:16-17, interpreting the former as a sign of allegiance to the Roman Church.
"The Roman Church has not relinquished her claim to supremacy; and when the world and the Protestant churches accept a sabbath of her creating, while they reject the Bible Sabbath, they virtually admit this assumption. They may claim the authority of tradition and of the Fathers for the change; but in so doing they ignore the very principle which separates them from Rome—that “the Bible, and the Bible only, is the religion of Protestants.” The papist can see that they are deceiving themselves, willingly closing their eyes to the facts in the case. As the movement for Sunday enforcement gains favor, he rejoices, feeling assured that it will eventually bring the whole Protestant world under the banner of Rome. GC 448.2"
"But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition?"
The EGW passage illustrates the principle in Matthew 15:3 by showing how Protestant churches, in accepting Sunday as the Sabbath, are transgressing God's commandment due to tradition, similar to the Pharisees in Jesus' time.
"it is commanded. But in the very act of enforcing a religious duty by secular power, the churches would themselves form an image to the beast; hence the enforcement of Sundaykeeping in the United States would be an enforcement of the worship of the beast and his image. GC 448.3"
"And he had power to give life unto the image of the beast, 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."
The EGW passage interprets the enforcement of a religious duty by secular power as forming an image to the beast, which aligns with the theme of the image of the beast in Revelation 13:15 demanding worship.