It is “the Book of Mormon term for the Melchizedek Priesthood, known to the ancients as the ‘Holy Priesthood, after the Order of the Son of God’ (D&C 107:2–4). This, ‘the holiest order,’ is the authority by which the gospel is administered in all dispensations (D&C 84:18–20). Accordingly, those called into the holy order of God had both the authority and responsibility to preach the word of God and perform ordinances … .
“President Ezra Taft Benson explained that to receive the highest blessings of the holy order is ‘the equivalent today of entering into the fulness of the Melchizedek Priesthood, which is only received in the house of the Lord’ [‘What I Hope You Will Teach Your Children about the Temple,’ 8]” (Largey, Book of Mormon Reference Companion, 334–35) .
The superscription to Alma 5 was part of the ancient record translated by the Prophet Joseph Smith and dictated by him to his scribe (see also, for example, 2 Nephi, Mosiah 9, and Alma 21).
“This [superscription] appeared in the 1830 [edition of the Book of Mormon]. … It is apparently from Mormon’s hand and is intended to introduce a quoted record. The original manuscript is not extant at this point (nor for similar introductions at the beginning of our chapters 7 and 9 of Alma).
“The printer’s manuscript indicates that these summaries were set off from the rest of the text only by a dash, with the first verse of the text beginning on the same line” (Gardner, Second Witness, 4:90).
The phrase in italics was introduced in the 2013 edition of the Book of Mormon. The 1981 edition had the phrase “Comprising chapter 5.”