In the sequential logic of Nephi's testimony, the mention of God leads to the covenants between God and Israel, Nephi's "fathers." The law of Moses might have fulfillment in Christ, but the covenant with Abraham endures.
Redaction analysis: The next transition is not as easily dependent upon the phrases immediately preceding them. While there are covenants with Abraham, the atonement ("eternal plan of deliverance from death") is not an obvious one. This theme, however, is prominent in Jacob's sermon. This suggests that Nephi is writing this transition either immediately after writing Jacob's sermon, or after re-reading the sermon. Therefore, this transition comes from the connection Nephi makes between his testimony of the Savior, Jacob's testimony, and the recent experience with Jacob's sermon on this subject.