"Who shall declare his generation?" This probably means, "Who will declare his birth, and who will declare where he has come from? Who will declare his origin, his beginning in the heavens before his coming to earth, and his instatement as the eternal Son generated by the Father?" His true genesis began back in eternity. In the premortal council, the plan of salvation was laid from the foundation of the world. The Nephites knew about this council and would hear more about it in Alma 13. In speaking to Noah’s priests, Abinadi said that, first, the prophets will declare his generation. The priests then asked Abinadi who the ones were who would "publish peace" (Mosiah 12:21). Abinadi’s answer was, "The ones who will declare his generation." Abinadi went on to say that, second, anyone who accepts the Atonement of Christ can declare his generation. Anyone who believes in that divine plan can declare this good news. We too can declare it and declare his generation.
The priests of Noah likely thought that Isaiah’s prophecy concerning those who publish peace was referring to them, or, at the very least, that it included them. After all, they were declaring the great tidings of riotous and lavish living. However, that is not what the good tidings are all about. The good tidings (the good news, the gospel) are about salvation, that the Son now reigns, and that he has redeemed his people. The word "peace" in Hebrew is shalom, which can also mean love and reconciliation. When the people have kept their covenants, the prophets can then declare that God and His people were now at peace one with another again, because his people have been redeemed and he has provided intercession for them.
Next, Mosiah 14:10 (Isaiah 53:10) declared, "Yet it pleased the Lord to bruise him." In a way, it pleased the Father that the Son was bruised for us, because "when thou shalt make his soul an offering for sin, he shall see his seed." The pronoun "thou (you)" in this scripture refers to us. The prophet explained that it pleased the Lord to bruise the Messiah, so that we have the opportunity to make his soul an offering. Then there will not be a lamb offering anymore; the Son fulfilled that symbolic act. However, now we can make his soul an offering for our sins. This will reconcile us in atonement with him, and then he [God the Father] will see his [the Son’s] seed. For we are now his seed, his sons and daughters, and that makes us reconciled as family members with the Father once again.
"He [the Father] shall then prolong his days and the pleasure of the Lord shall prosper in his hand" (Mosiah 14:10; Isaiah 53:10). Abinadi applied that couplet to the resurrection of Christ, for after Christ’s death, "the Lord will prolong his days," and he will come back to life and "shall prosper in his hand." That prosperity will then allow us to receive a division of the spoil, the goods captured in battle, that is talked about in in Isaiah 53:12. In this way, Abinadi said, every nation will see and know. And that, of course, goes back to and answers the question the priests had asked about the "generation" or the full becoming of this deified servant.