This is a promise that the house of Israel, wherever the remnants may be, shall come to the knowledge of the true Messiah, after the Gentiles have received the Gospel.
On April 3, 1836, at the Kirtland temple, the prophet Joseph Smith and Oliver Cowdery had, as will be remembered, four glorious visions. They saw the Lord and received from him the assurance that he had accepted the temple, built to his name. Then “the heavens were again opened unto us; and Moses appeared before us, and committed unto us the keys of the gathering of Israel from the four parts of the earth, and the leading of the ten tribes from the land of the north.” (D. & C. 110:11) And thus began the fulfilment of this part of the prediction of Lehi in the Valley of Lemuel.