What is sin?

"John saw the fate of those who choose the path of transgression: "And the kings of the earth, and the great men, and the rich men, and the chief captains, and the mighty men, and every bondman, and every free man, hid themselves in the dens and in the rocks of the mountains; and said to the mountains and rocks, Fall on us, and hide us from the face of Him that sitteth on the throne, and from the wrath of the Lamb: for the great day of His wrath is come; and who shall be able to stand?" (Revelation 6:15-17).
     A terrible doom awaits the sinner, and therefore it is necessary that we know what sin is, in order that we may escape from its power. John says, "Whosoever committeth sin transgresseth also the law; for sin is the transgression of the law" (1 John 3:4). Here we have the true definition of sin; it is "the transgression of the law." How often the sinner is urged to leave his sins, and come to Jesus; but has the messenger who would lead him to Christ clearly pointed out the way? Has he clearly pointed out the fact that "sin is the transgression of the law," and that he must repent and forsake the breaking of God's commandments? . . .      God could not alter one jot or tittle of His holy law to meet man in his fallen condition; for this would reflect discredit upon the wisdom of God in making a law by which to govern heaven and earth. But God could give His only-begotten Son to become man's Substitute and Surety, to suffer the penalty that was merited by the transgressor, and to impart to the repentant soul His perfect righteousness. Christ became the sinless sacrifice for a guilty race, making men prisoners of hope, so that through repentance toward God because they had broken His holy law, and through faith in Christ as their Substitute, Surety, and righteousness, they might be brought back to loyalty to God and to obedience to His holy law. " FW 117