1 Nephi 15:3

For he truly spake many great things unto them,

which were hard to be understood,

save a man should inquire of the Lord;

and they being hard in their hearts,

therefore they did not look unto the Lord as they ought.

which were hard to be understood,

to - 31 occurrences in 18 verses - 1 Nephi 15:1, 2, 3, 4, 5, 6, 14, 17, 18, 19, 20, 21, 23, 24, 25, 32, 33, 35

to be - 3 occurrences in 3 verses - 1 Nephi 15:3, 33, 35