Boyd K. Packer discusses initiatory ordinance in his book on the temple.
Boyd K. Packer, The Holy Temple (Salt Lake City: Bookcraft, 1980), 154–155
The ordinances of washing and anointing are referred to often in the temple as initiatory ordinances. It will be sufficient for our purposes to say only the following: Associated with the endowment are washings and anointings—mostly symbolic in nature, but promising definite, immediate blessings as well as future blessings. Concerning these ordinances the Lord has said, “I say unto you, how shall your washings be acceptable unto me, except ye perform them in a house which you have built to my name?” (D&C 124:37).
And again: "I say unto you, that your anointings, and your washings . . . are ordained by the ordinance of my holy house." (D&C 124:39.)