This is the particular prophecy that triggers the statement of the Lord recorded in 3 Nephi:
3 Nephi 23:7-12
7 And it came to pass that he said unto Nephi: Bring forth the record which ye have kept.
8 And when Nephi had brought forth the records, and laid them before him, he cast his eyes upon them and said:
9 Verily I say unto you, I commanded my servant Samuel, the Lamanite, that he should testify unto this people, that at the day that the Father should glorify his name in me that there were many saints who should arise from the dead, and should appear unto many, and should minister unto them. And he said unto them: Was it not so?
10 And his disciples answered him and said: Yea, Lord, Samuel did prophesy according to thy words, and they were all fulfilled.
11 And Jesus said unto them: How be it that ye have not written this thing, that many saints did arise and appear unto many and did minister unto them?
12 And it came to pass that Nephi remembered that this thing had not been written.
The recording of the fulfillment of this particular prophecy is important as it confirms the power of the resurrection of the Messiah to bring life to the dead, to break the bands of death.