What meaneth the rod of iron which our father saw, that led to the tree?

the - 131 occurrences in 36 verses - 1 Nephi 15:1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36

the tree - 4 occurrences in 4 verses - 1 Nephi 15:21, 22, 23, 28