1 Nephi 21

The Lord covenanted with Abraham -

"...I will make of thee a great nation, and I will bless thee above measure, and make thy name great among all nations, and thou shalt be a blessing unto thy seed after thee, that in their hands they shall bear this ministry and Priesthood unto all nations;
10 And I will bless them through thy name; for as many as receive this Gospel shall be called after thy name, and shall be accounted thy seed, and shall rise up and bless thee, as their father..." (Pearl of Great Price | Abraham 2:9 - 10)

Since those days, the responsibility of the descendents of Israel was always intended to teach and bless the lives of all people and nations by preaching the gospel of Jesus Christ. Though at times, the children of Israel have also failed, it is Isaiah that reminds Israel that this covenant and responsibility has not changed as he writes -

"...Hearken, O ye house of Israel, all ye that are broken off and are driven out because of the wickedness of the pastors of my people; yea, all ye that are broken off, that are scattered abroad, who are of my people, O house of Israel. Listen, O isles, unto me, and hearken ye people from far; the Lord hath called me from the womb; from the bowels of my mother hath he made mention of my name." (Book of Mormon | 1 Nephi 21:1)

In other words, "from the bowels of my mother" means that almost from the beginning it is Israel's jobe to preach His name and His gospel. This does not apply only to the preaching to scattered Israel but to all people for -

"...It is a light thing (or not enough)that thou shouldst be my servant to raise up the tribes of Jacob, and to restore the preserved of Israel. I will also give thee for a light to the Gentiles, that thou mayest be my salvation unto the ends of the earth." (Book of Mormon | 1 Nephi 21:6)

As we learn of our lineage in patriarchal blessings, especially "Ephraim", this is the very responsibility we have having the blood of Israel.