The ministry of the Lord was confined to Israel, except in the special cases where those of other nations by exceeding faith sought him for blessings. Why did the gospel go to the house of Israel (and descendants of Abraham) ahead of the Gentiles?
Elder McConkie has an interesting statement regarding this: "...the house of Israel is composed of the spirits from preexistence who there developed a talent for spirituality, and who are therefore entitled to the blessings of heaven in this life on a preferential basis. All men, in due course, either in his life or in the spirit world, will be offered the blessings of salvation. But there is an eternal system of priorities; there is a law of election, a doctrine of foreordination; and Israel is entitled to the blessing of the holy word ahead of their Gentile fellows. During his lifetime Jesus took the gospel and its blessings, with isolated exceptions, to his kinsmen in Israel; after his resurrection he [sent] his apostolic witnesses to all men, irrespective of creed or race or ancestry. The Lord Jehovah—Jesus in the flesh—is simply conforming to the eternal law of gospel priorities that he and his Father ordained from before the foundations of the world." (Mortal Messiah, 3:11-12)
The aspect of this "preference", however, that Elder McConkie doesn't make clear is that it becomes the responsibility of those of the House of Israel who have received the blessing of the gospel to share it with the Gentiles.
