Mission calls did not originate with Joseph Smith. The Lord commanded, "Go ye into all the world, and preach the gospel to every creature" (Mark 16: 15). Most mission calls that came through Joseph Smith came by direct revelation, such as those called in June 1831 (see D&C 52). "Souls are as precious in the sight of God as they ever were," Joseph once explained, "and the Elders were . . . called to . . . persuade and invite all men everywhere to repent, that they may become the heirs of salvation" (History of the Church, 2:229).
Hyrum Smith offered this counsel: "God has commanded you to preach repentance to this generation; and if this generation will not receive the first principles of the Gospel and the Book of Mormon, they will receive nothing greater. Just go and do as you are told and God will bless you. It is the power of God that is going to convert the world, and nothing but the power of God. . . . It is the honest and pure in heart that will hearken to the everlasting covenant" (History of the Church, 6:320; paragraph divisions altered).