Nephi declares the religious orientation of his people. As a few of them were Old World Jews and had lived the Law in Jerusalem, this is not completely surprising. However, it is interesting that Nephi's experiences did not lead him to make major adaptations in the practice of religion. Unquestionably the clear revelation of the coming Savior flavored Nephi's and Jacob's teachings. Nevertheless, regardless of the teachings, the practice was Mosaic. For Nephi, the practice of religion would have been intimately bound up with the institutions of the Mosaic Law. He would have seen no conflict between the continuation of those practices and the teaching of a Christ who would eventually supercede those laws.
It is also historically significant that Nephi would establish his new colony on a religious model. This early declaration of their religious practices not only discusses their religion, but the entire basis upon which their society was based. We might expect that all early forms of social interaction in the band would be governed by the model that Nephi remembered from his youth.
The exigencies of the new life would certainly lead to adaptations of the Old World model, but for the time being, it is most likely that questions of leadership, worship, land management, and social organization would be answered by deference to the Law of Moses and the Jerusalem model (if they made any distinction between the two at all).