The Doctrine and Covenants is a book of scripture used by The Church of Jesus Christ of Latter-day Saints, whose members are often called Mormons. The book contains the revelations and commandments given to mankind through modern prophets and teaches us the modern applications of many essential topics, including missionary work. A revelation given to Joseph Smith in 1832 said:
Behold, I sent you out to testify and warn the people, and it becometh every man who hath been warned to warn his neighbor (Doctrine and Covenants 88:81).
Missionary work has been a critical part of the gospel of Jesus Christ. Jesus spent three years teaching the gospel and after His death, his disciples continued the work, traveling to many nations to share their message of the atonement of Jesus Christ. A modern Mormon apostle, explained:
Missionary work isn’t the only thing we need to do in this big, wide, wonderful Church. But almost everything else we need to do depends on people first hearing the gospel of Jesus Christ and coming into the faith. Surely that is why Jesus’s final charge to the Twelve was just that basic—to “go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost.” Then, and only then, can the rest of the blessings of the gospel fully come… (See Jeffrey R. Holland, We are All Enlisted, General Conference, October 2011.)
Missionary work is often a focus of the Doctrine and Covenants because many of the revelations sent Mormon men on missions. In those early days of the church, many adult men, both married and single, served missions. They traveled, usually on foot if they were assigned to the United States, preaching along the way to their assigned destinations. There are many accounts of large numbers of people being converted at a time. Those who served faithfully frequently found their lives enhanced by many blessings. Those who considered the Savior’s command that we teach the gospel to be a burden often found their lives challenging and unhappy. They sometimes learned that our happiness in life comes from doing what the Lord asks of us and in helping others find what we were fortunate enough to find.
15 And if it so be that you should labor all your days in crying repentance unto this people, and bring, save it be one soul unto me, how great shall be your joy with him in the kingdom of my Father!
16 And now, if your joy will be great with one soul that you have brought unto me into the kingdom of my Father, how great will be your joy if you should bring many souls unto me! (Doctrine and Covenants 18).