3 Nephi 28
Somehow I had never connected that the promises to each of the Twelve Disciples were given at this separate, private visitation by the Savior and not during the three days of instruction where many people were present. I had envisioned that the promise was made at the large gathering as part of one of the times when he spoke specifically to the people. I get the impression that this same scene took place among the Twelve Apostles before the crucifiction. (I would guess at the last supper after Judas had left.) The difference being that all the Apostles besides John did not express a unanimous wish such as the nine Disciples.
If Timothy was one of the three then he had already endured the pains of death and this promise would be that he would never again endure the pains of death.
To know and recognize the three Nephites requires that we be covenant individuals because the Gentiles, and even the Jews shall not know them even as they work among them.