These ideas did not originate with the Prophet Joseph Smith. For example, when Jesus Christ spoke of the “mysteries of the kingdom,” he also alluded to temple matters. Margaret Barker, writes:
…Jesus’ parables were more than simple stories. “To you,” he said to his closest disciples, “has been given the secret of the Kingdom of God, but for those outside, everything is in parables.”Though differing somewhat in their terminology, the writings of Philo Judaeus, an important Jewish priest in the first century AD, and those within the New Testament book of Hebrews share similar distinctions in their description of a lower and higher priesthood, and their corresponding “mysteries.” In broad strokes, the significant contrast in both cases is between the lesser and the greater priesthood and their corresponding rites; in other words, between the Levitical priesthood (as described in Hebrews)—roughly corresponding to the Lower Mystery of Aaron (as described by Philo)—and the Melchizedek priesthood of Christ (in Hebrews)—analogous to the Higher Mystery of Moses (in Philo). In both cases, what characterizes the greater rites is that they bring the initiate beyond the veil into the presence of God, and there invest him with an eternal priesthood and kingship in the likeness of the Divine.
Secrets and mysteries were characteristic of temple tradition, and were the exclusive preserve of the high priesthood, who were permitted to enter the Holy of Holies.