Summary of previous Book of Mormon themes in Moroni 10

Moroni 10:19-21 and 24-31 has a lot of previous Book of Mormon themes and phrases weaved into it. Below is the text in full with relevant references in italics in between. Moroni draws particularly from Mormon 9 (his own earlier written text) and Moroni 7 (his father's sermon), but also gets inspiration from Nephi's farewell speech.

Different themes in Moroni 10 with their counterpart in italics are marked with a certain color. In two cases, themes are also repeated (red and orange), in which case the reference to the other relevant BoM passage is not repeated.

I know it may look a bit messy, but it goes to show the extent of Moroni's use of other Book of Mormon expressions and themes in this passage.

19 And I would exhort you, my beloved brethren, that ye remember that he is the same yesterday, today, and forever,

(Mormon 9:9: “God is the same yesterday, today, and forever”)

and that all these gifts of which I have spoken, which are spiritual, never will be done away,

(Mormon 9:7: “I speak unto you who deny the revelations of God, and say that they are done away, that there are no revelations, nor prophecies, nor gifts”)

even as long as the world shall stand

only according to the unbelief of the children of men.

(Mormon 9:20: “And the reason why he ceaseth to do miracles among the children of men is because that they dwindle in unbelief”)

20 Wherefore, there must be faith; and if there must be faith there must also be hope; and if there must be hope there must also be charity.

21 And except ye have charity ye can in nowise be saved in the kingdom of God; neither can ye be saved in the kingdom of God if ye have not faith; neither can ye if ye have no hope.

(Moroni 7:42-44: “if a man have faith he must needs have hope… wherefore he must needs have charity”.)
...

24 And now I speak unto all the ends of the earth—that if the day cometh that the power and gifts of God shall be done away among you, it shall be because of unbelief.

25 And wo be unto the children of men if this be the case; for there shall be none that doeth good among you, no not one. For if there be one among you that doeth good, he shall work by the power and gifts of God.

(Moroni 7:16: “every thing which inviteth to do good, and to persuade to believe in Christ, is sent forth by the power and gift of Christ”)

26 And wo unto them who shall do these things away and die, for they die in their sins, and they cannot be saved in the kingdom of God; and I speak it according to the words of Christ; and I lie not.

27 And I exhort you to remember these things; for the time speedily cometh that ye shall know that I lie not, for ye shall see me at the bar of God; and the Lord God will say unto you: Did I not declare my words unto you, which were written by this man,

(2.Nephi 33:11: "And if they are not the words of Christ, judge ye—for Christ will show unto you, with power and great glory, that they are his words, at the last day; and you and I shall stand face to face before his bar; and ye shall know that I have been commanded of him to write these things, notwithstanding my weakness.")

like as one crying from the dead, yea, even as one speaking out of the dust?

(Mormon 9:30: "I speak unto you as though I spake from the dead")
(2.Nephi 33:13: "And now, my beloved brethren, all those who are of the house of Israel, and all ye ends of the earth, I speak unto you as the voice of one crying from the dust")

28 I declare these things unto the fulfilling of the prophecies. And behold, they shall proceed forth out of the mouth of the everlasting God; and his word shall hiss forth from generation to generation.

(2.Nephi 29:2: "the words of your seed should proceed forth out of my mouth unto your seed; and my words shall hiss forth unto the ends of the earth")

29 And God shall show unto you, that that which I have written is true.

30 And again I would exhort you that ye would come unto Christ, and lay hold upon every good gift, and touch not the evil gift, nor the unclean thing.

(Moroni 7:8, 19: "For behold, if a man being evil giveth a gift, he doeth it grudgingly; wherefore it is counted unto him the same as if he had retained the gift; wherefore he is counted evil before God... lay hold upon every good thing")

31 And awake, and arise from the dust, O Jerusalem; yea, and put on thy beautiful garments, O daughter of Zion; and strengthen thy stakes and enlarge thy borders forever, that thou mayest no more be confounded, 

(Isaiah 52:1-2 / 2.Nephi 8:24-25: "Awake, awake, put on thy strength, O Zion; put on thy beautiful garments, O Jerusalem, the holy city; for henceforth there shall no more come into thee the uncircumcised and the unclean. Shake thyself from the dust; arise, sit down, O Jerusalem; loose thyself from the bands of thy neck, O captive daughter of Zion.")

that the covenants of the Eternal Father which he hath made unto thee, O house of Israel, may be fulfilled.

(3.Nephi 20:12: "then is the fulfilling of the covenant which the Father hath made unto his people, O house of Israel.") NB! Isaiah 52:1-2 is also quoted in 3. Nephi 20, which also ties these last two themes together.

Clearly, Moroni studied the plates he had in his possession and drew a lot of inspiration from there when wrapping up with his last words. In addition, he restates some of the things he already wrote in Mormon 9, which he thought would be his last words at the time he wrote it (see Moroni 1:4).

Perhaps the plates of Mormon with the small plates of Nephi attached were the only ones he had at least regular or permanent access to? Wandering around for years, he was likely not dragging all the Nephite records around.