All things bear record · Doctrine and Covenants
2 witnesses of Christ here, and 6 further echoes from the reading.
And now, behold, this shall you say unto him—he who spake unto you, said unto you: I, the Lord, am God, and have given these things unto you, my servant Joseph Smith, Jun., and have commanded you that you should stand as a witness of these things; Doctrine and Covenants 5:2
The Lord gives Joseph words to tell Martin: the One who gave him the plates is God Himself.
And to none else will I grant this power, to receive this same testimony among this generation, in this the beginning of the rising up and the coming forth of my church out of the wilderness—clear as the moon, and fair as the sun, and terrible as an army with banners. Doctrine and Covenants 5:14
Christ calls it "my church" and describes it with the words used of the bride in the Song of Solomon, an image of the Church as the Savior's bride coming out of the wilderness of apostasy.
How we know: a footnote points to Him · a Church study aid lists it
And behold, whosoever believeth on my words, them will I visit with the manifestation of my Spirit; and they shall be born of me, even of water and of the Spirit— Doctrine and Covenants 5:16
Believers are spiritually reborn as Christ's own children through baptism and the Holy Ghost.
For a desolating scourge shall go forth among the inhabitants of the earth, and shall continue to be poured out from time to time, if they repent not, until the earth is empty, and the inhabitants thereof are consumed away and utterly destroyed by the brightness of my coming. Doctrine and Covenants 5:19
In His own voice Christ speaks of "my coming," whose glory will consume the unrepentant wicked.
How we know: a footnote points to Him · a Church study aid lists it
Behold, I tell you these things, even as I also told the people of the destruction of Jerusalem; and my word shall be verified at this time as it hath hitherto been verified. Doctrine and Covenants 5:20
The same Lord who foretold Jerusalem's destruction, as Jehovah through His prophets and in person during His ministry, says His warnings will come true again.
And that you be firm in keeping the commandments wherewith I have commanded you; and if you do this, behold I grant unto you eternal life, even if you should be slain. Doctrine and Covenants 5:22
Only the Savior can grant eternal life. Here He promises it to Joseph, foreshadowing Joseph's martyrdom.
And now, except he humble himself and acknowledge unto me the things that he has done which are wrong, and covenant with me that he will keep my commandments, and exercise faith in me, behold, I say unto him, he shall have no such views, for I will grant unto him no views of the things of which I have spoken. Doctrine and Covenants 5:28
The condition for Martin's witness is humility, covenant, and faith centered in Christ Himself.
And if thou art faithful in keeping my commandments, thou shalt be lifted up at the last day. Amen. Doctrine and Covenants 5:35
Christ promises the faithful they will be raised up and exalted at the last day, just as He promised in His mortal and Nephite ministries.