“Nothing Shall Overthrow It, Save… Transgression”

Joseph F. McConkie, Robert L. Millet
We would understand this statement to mean that the Nephite Church could not be destroyed by external influences. Indeed it appears that in past dispensations-most notably the meridian of time-when the Church has been lost the cause has been wickedness and error within the Church rather than opposition from without.

Doctrinal Commentary on the Book of Mormon, Vol. 2