As Alma expresses his joy over the sons of Mosiah still being “his brethren in the Lord” (v. 2), he gives us two parts of a four part formula for being a successful missionary. We will discuss these two parts here and add the other two parts in subsequent discussions.
The first requirement of a successful missionary is that he has a knowledge of the truth (v. 2). It has been said that the difference between an effective missionary and an unhappy one is about three inches, the depth of the standard works of which he or she has or has not a knowledge. The Bible and the Triple Combination are called the standard works because they give us the standard by which truth is measured. Isaiah urged his people (around 700 B.C.): “To the law [of Moses] and to the testimony [of the prophets]; and if they speak not according to this word, it is because there is no light in them” (2 Nephi 18:20; Isaiah 8:20). Elder Ezra Taft Benson quoted this scripture as a key for not being deceived and said that this great truth from Isaiah was so important that it was included in the Book of Mormon. The sons of Mosiah were men of sound understanding because they had searched the scriptures diligently that they might know the word of God (Alma 17:2).
The second requirement for becoming an effective missionary, as given by Alma, is much prayer and fasting. The blessings of fasting and prayer are having the spirit of prophecy and the spirit of revelation (v. 3). “The testimony of Jesus is the spirit of prophecy” (Revelation 19:10). The spirit of revelation is the Lord telling “you in your mind and in your heart, by the Holy Ghost” (D&C 8:2–3). To know in your mind is to know intellectually. To know in your heart is to have testimony borne to your spirit. The intellect without the Spirit may be deceived, and the spirit of the individual may be deceived by emotion if the intellect does not also receive a witness. When these two witnesses go hand in hand, the result is being able to teach “with power and authority of God” (Alma 17:3). When Jesus taught during his earthly ministry “they were astonished by his doctrine [intellect]: for he taught as one having authority [testimony]; and not as the scribes” Matthew 5:29). This manner of teaching brought much success to the sons of Mosiah among the Lamanites (Alma 17:4). Missionary work had not been easy, however. They had suffered both physically and mentally in obtaining this success (v. 5).