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).
The Son of God spoke to Moses from the mountaintop. God made the rocks His sanctuary. His temple was the everlasting hills. The Divine Legislator descended upon the rocky mountain to speak His law in the hearing of all the people, that they might be impressed by the grand and awful exhibition of His power and glory, and fear to transgress His commandments. God spoke His law amid thunders and lightnings and the thick cloud upon the top of the mountain, and His voice was as the voice of a trumpet exceeding loud. The law of Jehovah 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.
While John was contemplating the scenes of Horeb, the Spirit of Him who sanctified the seventh day came upon him. He contemplated the sin of Adam in transgressing the divine law, and the fearful result of that transgression. The infinite love of God, in giving His Son to redeem a lost race, seemed too great for language to express. As he presents it in his Epistle he calls upon the church and the world to behold it. “Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not” (1 John 3:1).
It was a mystery to John that God could give His Son to die for rebellious man. And he was lost in amazement that the plan of salvation, devised at such a cost to Heaven, should be refused by those for whom the infinite sacrifice had been made....
It is no light matter to sin against God, to set the perverse will of man in opposition to the will of his Maker. It is for the best interest of men, even in this world, to obey God’s commandments. And it is surely for their eternal interest to submit to God, and be at peace with Him.... God made him a free moral agent, to obey or disobey. The reward of everlasting life—an eternal weight of glory—is promised to those who do God’s will.—The Sanctified Life, 74-76. RC 95
In like manner the disciples were to seek blessings from God. In the feeding of the multitude and in the sermon on the bread from heaven, Christ had opened to them their work as His representatives. They were to give the bread of life to the people. He who had appointed their work, saw how often their faith would be tried. Often they would be thrown into unexpected positions, and would realize their human insufficiency. Souls that were hungering for the bread of life would come to them, and they would feel themselves to be destitute and helpless. They must receive spiritual food, or they would have nothing to impart. But they were not to turn one soul away unfed. Christ directs them to the source of supply. Pr 305
"I was in the Spirit on the Lord's day, and heard behind me a great voice, as of a trumpet," Revelation 1:10 (King James Version)