Narrative: This verse is part of Nephi’s transition from the theme of the discourse to his final testimony. It serves as a pivot point in his narrative. He connects the theme he had ended on - those of his people who were “unbelievers” and “wicked” who were unable to understand the Spirit. He moves from that specific context of his own people to a generalization of this problem to future peoples. Among those people also will be those whose hearts are hardened “against the Holy Spirit” and the effect will be that they are unable to believe in things that are written.
Nephi here makes a parallel between his contemporary people who are unable to accept the Spirit when it is presented orally, and with power, to those future people who will be unable to discern the spirit in the written word of God - in particular, the words of Nephi’s book.