Mormon added the necessity of baptism in order to lay hold of the gospel of Jesus Christ to his list of four things to know. There are two sources to learn the gospel of Jesus Christ: the record Mormon is keeping, the Book of Mormon, and the record that shall come from the Jews, the Bible. The remnants of the Nephites and the Lamanites will also receive the Bible from the Gentiles (v. 8). Jesus ministered to the Jews in Jerusalem and other cities in the land. The apostles kept a record. The record contained the fullness of the gospel in which they bore testimony of “truth which is in the Lamb of God” (1 Nephi 13:24). The Bible was passed on to the Gentiles who disseminated it to the Lamanites.
The Book of Mormon was written to testify to the Lamanites of the teachings that are also found in the Bible. If they believe the Bible, they will also believe the Book of Mormon (Mormon 7:9). Thus, as Ezekiel testified, the two books “shall become one in thine hand” (Ezekiel 37:16–17). Joseph of Egypt also testified that the two records would “grow together unto the confounding of false doctrines, and laying down of contentions, and establishing peace among the fruit of thy loins, and bringing them to the knowledge of their fathers in the latter days; and also to a knowledge of my covenants, saith the Lord” (2 Nephi 3:12). As the two are studied together, they will become interpreted and understood as teaching the same gospel of Jesus Christ.
One of the purposes of the Book of Mormon is to prove “to the world that the holy scriptures are true” (D&C 20:11). Both books teach the same doctrines. In the words of President Harold B. Lee: “Many doctrines of the Bible that are only partially covered there are beautifully explained in the Book of Mormon, the Doctrine and Covenants, and the Pearl of Great Price.” Both Mormon and Joseph of Egypt bore witness of the Book of Mormon bringing the Nephite remnant to a knowledge of their fathers (Mormon 7:9). Joseph of Egypt adds that they will come to a knowledge of the covenants of the Lord (see 2 Nephi 3:12). Mormon also adds that they will be of the first covenant (Abraham), and that the Nephite remnant will know they are a remnant of Joseph (Mormon 7:9)—the answer to the question Mormon asked earlier (see v. 2 above). He further qualified the need of baptism; first with water, and then with fire and the Holy Ghost. In complying with these baptisms, they will be following the example set by the Savior himself (see 2 Nephi 31:6–10). These actions through faith will benefit all of us in the day of Judgment (Mormon 7:10).