The well-known Old Testament scripture in Isaiah 52:7 reads:
How beautiful upon the mountains are the feet of him that bringeth good tidings, that publisheth peace; that bringeth good tidings of good, that publisheth salvation; that saith unto Zion, Thy God reigneth!
In the Book of Mormon, Abinadi teaches this scripture in King Noah’s court however he gives a specific understanding of it. In Mosiah 15 he says that “all the holy prophets ever since the world began” are “they who have published peace, who have brought good tidings of good, who have published salvation; and said unto Zion: Thy God reigneth!”
However he also goes on to say in verse 18
And behold, I say unto you, this is not all. For O how beautiful upon the mountains are the feet of him that bringeth good tidings, that is the founder of peace, yea, even the Lord, who has redeemed his people; yea, him who has granted salvation unto his people;
In his interpretation of the Isaiah scripture, Abinadi sees both the Lord and the prophets as those who “redeems his people, and the prophets he sends to preach salvation and peace”.
John A. Tvedtnes explains:
This interpretation is strikingly similar to the one found in one of the Dead Sea Scrolls, 11QMelchizedek (also known as 11Q13), which cites the Isaiah passage, then explains that “the mountains are the pro[phets . . . ] And the messenger is [the ano]inted of the spirit about whom Dan[iel] spoke [ . . . and the messenger of] good who announces salv[ation is the one about whom it is written that] he will send him ‘to comfo[rt the afflicted, to watch over the afflicted ones of Zion’].” The Hebrew term rendered “anointed” here is masiah, Messiah. The interpretation of the Isaiah passage in the scroll agrees with Abinadi’s teachings in mentioning both the Messiah and the prophets.– John A. Tvedtnes, “Ancient Texts in Support of the Book of Mormon,” in Echoes and Evidences of the Book of Mormon, edited by Donald W. Parry, Daniel C. Peterson, and John W. Welch (Provo, Utah: FARMS, 2002), Chapter 8
Where would Joseph have found this interpretation of Isaiah?