“Other sheep” is a phrase Jesus used in John 10:16, where he spoke of sheep “not of this fold” whom he must also bring, so that there would be “one fold, and one shepherd” (John 10:16). During his post-resurrection ministry among the Nephites, he told them that they were the people he had meant: “ye are they of whom I said: Other sheep I have which are not of this fold” (3 Nephi 15:21). He explained that the Father had not permitted him to tell the Jews at Jerusalem about the Nephites or about the other tribes of Israel led away from that land; the Jews supposed the other sheep meant the Gentiles, and misunderstood (3 Nephi 15:14-23).
Jesus then identified a further group of other sheep, distinct from the Nephites and from those at Jerusalem—people who had not yet heard his voice and to whom he had never manifested himself. He had a commandment from the Father to go to them so that they too would be numbered among his sheep, “that there may be one fold and one shepherd” (3 Nephi 16:1-3). He afterward stated that he would go to show himself to the lost tribes of Israel (3 Nephi 17:4).