"A Sabbathkeeper The Lord's day mentioned by John was the Sabbath, the day on which Jehovah rested after the great work of creation, and which He blessed and sanctified because He had rested upon it. The Sabbath was as sacredly observed by John upon the Isle of Patmos as when he was among the people, preaching upon that day. By the barren rocks surrounding him, John was reminded of rocky Horeb, and how, when God spoke His law to the people there, He said, “Remember the sabbath day, to keep it holy” ( Exodus 20:8 ). SL 74"
"Remember the sabbath day, to keep it holy."
EGW directly quotes Exodus 20:8.
"In the surroundings of his island home the exiled prophet read the manifestations of divine power, and in all the works of nature held communion with his God. The most ardent longing of the soul after God, the most fervent prayers, went up to heaven from rocky Patmos. As John looked upon the rocks, he was reminded of Christ, the rock of his strength, in whose shelter he could hide without a fear. SL 74.1"
"The Lord is my rock, and my fortress, and my deliverer; my God, my strength, in whom I will trust; my buckler, and the horn of my salvation, and my high tower."
Both passages use the imagery of a rock as a symbol of God's strength and refuge.
"was unchangeable, and the tablets upon which He wrote that law were solid rock, signifying the immutability of His precepts. Rocky Horeb became a sacred place to all who loved and revered the law of God. SL 74.3"
"And he wrote on the tables, according to the first writing, the ten commandments, which the Lord spake unto you in the mount out of the midst of the fire in the day of the assembly: and the Lord gave them unto me."
Both passages refer to the tablets of stone upon which the Ten Commandments were written, emphasizing their permanence and the immutability of God's law. While not a direct quote, the connection is clear and meaningful.