Moroni extracts from the record these choice words of the Savior concerning a fundamental priesthood function—how to bestow the Holy Ghost upon those who are worthy to receive this gift. The book of 3 Nephi includes many references to the Holy Ghost. Of the most relevance to the material in Moroni chapter 2 is the following:
And it came to pass that when Jesus had made an end of these sayings, he touched with his hand the disciples whom he had chosen, one by one, even until he had touched them all, and spake unto them as he touched them.
And the multitude heard not the words which he spake, therefore they did not bear record; but the disciples bare record that he gave them power to give the Holy Ghost. And I will show unto you hereafter that this record is true.
And it came to pass that when Jesus had touched them all, there came a cloud and overshadowed the multitude that they could not see Jesus. (3 Nephi 1:36–38)
Third Nephi does not contain the actual words spoken by the Savior in conferring this power and authority upon His disciples. Therefore, it is a great service that Moroni performs in providing from the record these significant words of the Lord Jesus Christ.