The gospel and the three angels’ messages are inseparable

Christ’s righteousness to be proclaimed—The message of Christ’s righteousness must be proclaimed from one end of the earth to the other. Our people are to be aroused to prepare the way of the Lord. The third angel’s message—the last message of mercy to a perishing world—is so sacred, so glorious. Let the light go forth as a lamp that burneth. Mysteries into which angels have desired to look, which prophets and kings and righteous men desired to know, the church of God is now to unfold.—Letter 404, 1907 (December 30)3AM 26.1

The message of Christ’s righteousness is to sound from one end of the earth to the other to prepare the way of the Lord. This is the glory of God, which closes the work of the third angel.—Testimonies for the Church 6:19 (1901)3AM 26.2

Preaching Christ includes preaching His truths—The present truth, the special message given to our world, even the third angel’s message, comprehends a vast field, containing heavenly treasures. No one can be excusable who says, I will no longer have anything to do with these special messages; I will preach Christ. No one can preach Christ, and present the truth as it is in Jesus, unless he presents the truths that are to come before the people at the present time, when such important developments are taking place.—Manuscript 33, 1897 (April 6) (The Voice in Speech and Song, 325, 326)3AM 26.3

God’s ordained means to restore His moral image in humanity—The Lord will not close up the period of probation until the message has been carried to the world. But we are to give the trumpet a certain sound, that the name of the Lord may be glorified.3AM 27.1

... A great work is to be done in setting before the world the saving truths of the gospel. This is His ordained means for stemming the tide of moral corruption. The message of the third angel is to go with power and is to be a means of restoring the moral image of God in man. The messages that are coming from heaven are the only power that will draw the hearts of the people of God together. He designs that these messages should be understood by the people as the last testing message that will be given to a fallen world.—Manuscript 175, 1907 (November 11)3AM 27.2

Proclaiming the whole gospel—In these last days it is our duty to ascertain the full meaning of the first, second, and third angels’ messages. All our transactions should be in accordance with the Word of God. The first, second, and third angels’ messages are all united, and are revealed in the 14th chapter of Revelation from the sixth verse to the close. The whole gospel is to be proclaimed throughout the world.—Manuscript 15, 1896 (April 27)3AM 27.3