The Savior is again testifying of his identity and authority in order that the people will look to him and his teachings for salvation. Since he was the Lawgiver to Moses, he commands the Nephites (and us) to hearken to the commandments and teachings that he has given to them in chapters 9 through 14.
He reminds them that all of the previous prophets, practices, laws and ordinances had testified of him-Jehovah, the Creator, the Redeemer, the Christ. Previously they had been obedient to the law, but now , Jesus commands them to he obedient to the Lawgiver. “I have given unto you the commandments; therefore keep my commandments.” See also commentary on 3 Nephi 9:19.