In verse 2 of this chapter, Benjamin declared that an angel had come to give him the message that he should reinforce the teaching of the coming mortal mission of the Messiah. Now he declares that he has done so. Verses 24 through 27 repeat the Lord’s words, which form his testimony of the message he was required to declare. Both as king and the spiritual leader of the people, this declaration of the divine desire stands as a witness to the people. It is, in Benjamin’s words, “a bright testimony against this people, at the judgment day.”
Why is it a testimony against his people? It is a matter of emphasis of the importance of the message. It is against the people only if they reject it. Only if they do not accept the atonement will they be in a state where a just God could no longer exercise mercy, because they would have rejected the foundations upon which the mercy might be given.
Why couch the final testimony in these words? It probably returns to the dramatic events of the war and the contentions which had led to so many dissensions by the Lamanites. There had been many who had rejected the testimony, and this is a warning for those who might still have some sympathy with them.
The very last sentence, ending in amen, sealed that final testimony, and also created the need to end the chapter on that point. Our current chapters 1 through 3 were all part of the original Chapter I of Mosiah, which ended with this testificatory amen.