Textual: We have a particular instance of the type of questioning of Abinadi by the priests. It appears that this is not the full questioning, but simply one that Mormon elects to include. Note that verse 19 has Abinadi withstanding questioning, with verse 20 starting with "and it came to pass." This would appear to indicate that what we have is a single response, and perhaps the concluding response, of the questioning.
The question of the priests cites Isaiah 52:7-10, with no changes from the text of the King James Version of those verses. The very stating of these verses tells us something important about the Zeniffite expedition. They clearly brought a copy of the brass plates (or at least some sections, with Isaiah being obviously one of the them). It is certain that the brass plates themselves would not have been allowed to leave Zarahemla, as they were part of the regnal insignia entrusted to Mosiah by Benjamin (Mosiah 1:16). The preparations for their departure must either have included the time to make a copy, or else there were multiple copies available in the community. That a copy was available for study rather than remembered text (even though this text is remembered, as there is no indication of consulting the text at this time) is evidenced by the change in the priests under Noah. Those who might have been charged with remembering scriptures were removed, and these new priests needed a way of learning the texts.
The last question that must be asked of this section of text is why this particular question was posed to Abinadi. We must suppose that since the priests of Noah were trying to "cross" Abinadi, that the question was not asked because they sincerely wanted to understand the answer. There must be some conflict hidden in the text which would show a difference between Abinadi and the priests that they could use against him. Thus somehow, this text is one where they saw a religious difference that they thought they could use to their advantage. What was it?
Of course we do not have sufficient information to know for certain, but there are some possibilities that can at least give us a frame in which we can see the verbal combat arising.
Context 1: Noah's people as a victorious Jerusalem versus Abinadi's future calamities. The text that is specifically cited deals with a triumphant Jerusalem. The watchmen are shouting for joy, and the Lord "hath comforted his people, he hath redeemed Jerusalem." In the context of the earlier victory over the Lamanites, Noah's realm appears to be in a period of peace. It would not be unusual for the priests to associate themselves with Jerusalem, and apply this verse to their present conditions. If the priests were using this text as a proof of the current protection of the Lord over their people, that would place Abinadi in a position of denying scripture. Thus in this context, the question is asked to contrast the current favor and peace with Abinadi's dire predictions. This is essentially the position John W. Welch takes:
Context 2: This context is a little harder to see, because it presumes that both the priests and Abinadi knew the surrounding context of the verses rather than the verses themselves. This is not hard to presume, as the appear to be able to cite scripture at will. When the particular text is cited, it comes with the implicit connections to the surrounding texts. Indeed, Abinadi's response strongly suggests that he understood this linkage to the larger context, because his response cites Isaiah 53, which is a continuation of the text message of 52 from which this text arises. If this is the context of the question, then we may be seeing a repeat of the Sherem/Jacob conflict. Abinadi's response clearly proclaims the Messiah. If Noah's priests understand the Law the way Sherem did, then they would preach the Law of Moses (as they proclaim in verse 28) but deny the role of the Messiah. With their Nephite heritage, however, they would surely have known of the Messianic emphasis of Nephite religion, and expected that Abinadi would interpret this text Messianically. We may presume that the priests would have denied the Messianic nature of the text, and used that conflict of interpretation to condemn Abinadi. See Jacob 7 for the debate between Jacob and Sherem. It is interesting to note that not only do we see a recurrence of the polygamy issue when these people return to the culture area of the land of Nephi, but also perhaps a return to the religious philosophy of Sherem, who was a man of that culture area. We may be seeing a particular form of religious synthesis adopted by the Lamanites of that particular region.